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InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 251. |
Have you ever seen a game of tug of war ? In this game two teams pull a rope in opposite direction. But sometimes the rope does not move explain why. |
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Answer» a) When two forces acts on an object in opposite direction then the net force is difference of two forces. b) If two teams pull the rope with equal force, the forces will be in opposite direction and will cancel with each other and the rope will not move. |
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| 252. |
If the force acting on a body is inversely proportional to its speed, the kinetic energy of the body isA. constantB. directly proportional to timeC. inversely proportional to timeD. directly proportional to square of time |
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Answer» Correct Answer - B `F prop 1/v` `F=lambda/v`, where `lambda` : constant `ma= m (dv)/(dt)=lambda/v implies m int_(0)^(v) dv =lambda int_(0)^(t) dt` `m|v^(2)/2|_(0)^(v) =lambda |t|_(0)^(t) implies 1/2 mv^(2)=K=lambda t` `K prop t` |
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| 253. |
The force of attraction between any two objects having mass isA) frictional B) muscular C) gravitational D) magnetic |
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Answer» C) gravitational |
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| 254. |
One or more forces are acting in the following examples. Name them.(1) Srikant is playing basketball(2) Raju rubs a peacock feather between pages of his notebook(3) When you rub the palm of your hands, you feel the heat on the palms(4) A blacksmith uses a hammer to beat the hot piece of iron(5) A cricketer hits the ball, but it stops just before the boundary line(6) We can walk on the road without falling down. |
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Answer» (1) Muscular force (2) Electrostatic force (3) Frictional force (4) Muscular force (5) Frictional force (6) Frictional force |
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| 255. |
What is the total normal force acting on a surface? |
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Answer» The normal force on the object is equal but in opposite direction to the gravitational force applied on the object (or the weight of the object), that is, where m is mass, and g is the gravitational field strength (about 9.81 m/s2 on Earth). |
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| 256. |
When a rubber sucker is pressed onto a flat glass surface, it sticks tightly on the surface. Why? You need a large force to separate it from the surface. Why? |
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Answer» When a rubber sucker is pressed onto a flat glass surface, practically all the air between the surfaces of the sucker and the glass is pushed out. The air pressure there becomes much less than the atmospheric pressure. Hence, the sucker sticks to the glass due to the external atmospheric pressure. The atmospheric pressure is about 105 Pa. It is very large. Hence, to work against it to separate the sucker from the glass, a large force is needed. |
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| 257. |
A body of mass 0.25 kg is projected with muzzle velocity `100 ms^(-1)` from a tank of mass 100 kg. What is the recoil velocity of the tank?A. `5 ms^(-1)`B. `25 ms^(-1)`C. `0.5 ms^(-10)`D. `0.25 ms^(-1)` |
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Answer» Correct Answer - D Using law of conservation of momentum, we get `100 xx v=0.25xx100 implies v=0.25 ms^(-1)` |
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| 258. |
When a body of mass `m_(1)` moving with uniform velocity `40 ms^(-1)` collides with another body of mass `m_(2)` at rest, then the two together begin to move with uniform velocity of `30 ms^(-1)`. The ratio of the masses (i.e., `m_(1)//m_(2)`) of the two bodies will beA. `1 : 3`B. `3 : 1`C. `1 : 1.33`D. `1 : 0.75` |
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Answer» Correct Answer - B Initial momentum of the system `=m_(1)xx40+m_(2) xx0=40 m_(1)` Final momentum of the system `=(m_(1)+m_(2))xx30` By the law of conservation of momentum, Initial momentum = Final momentum `40 m_(1) =(m_(1)+m_(2))30` `40 m_(1)-30 m_(1) =30 m_(2)` `10 m_(1) = 30 m_(2) implies m_(1)/m_(2) =3/1` |
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| 259. |
A uniform metre rule of weight 10gf is pivoted at its 0 mark.(i) What moment of force depresses the rule?(ii) How can it be made horizontal by applying a least force? |
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Answer» (i) Anticlockwise moment= 10gf × 50 cm = 500gf cm (ii) From the principle of moments, Anticlockwise moment = Clockwise moment 10gf × 50 cm = W × 100cm So, W = 10gf x 50cm/100cm = 5gf By applying a force 5 gf upwards at the 100 cm mark, rule can be made horizontal |
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| 260. |
What happens when you hold the two ends of a spring and pull them apart? |
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Answer» Its shape changes due to the force exerted by pull. |
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| 261. |
Which of the following has greater inertia. (a) 50 paisa coin (b) one rupee coin (c) five rupee coin |
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Answer» (c) five rupee coin has greater inertia. |
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| 262. |
What is the S.I. unit of work? Define it. |
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Answer» The S.I. unit of work is newton-metre or joule (J). 1Joule = 1N × 1m. 1J of work is said to be done by a force of 1N if it displaces a body by 1m in the direction of force. |
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| 263. |
State S.I. unit of power and define it. |
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Answer» S.I. unit of power is J/s or Js-1 (or watt W). The power is said to be 1 watt when 1J of work is done in 1sec. |
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| 264. |
What are the Examples of Newton’s Third Law of Motion? |
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Answer» Newton’s Third Law of Motion states that there is always reaction for every action in opposite direction and of equal magnitude. Example: (a) Walking of a person - A person is able to walk because of the Newton’s Third Law of Motion. During walking, a person pushes the ground in backward direction and in the reaction the ground also pushes the person with equal magnitude of force but in opposite direction. This enables him to move in forward direction against the push. (b) Recoil of gun - When bullet is fired from a gun, the bullet also pushes the gun in opposite direction, with equal magnitude of force. This results in gunman feeling a backward push from the butt of gun. (c) Propulsion of a boat in forward direction – Sailor pushes water with oar in backward direction; resulting water pushing the oar in forward direction. Consequently, the boat is pushed in forward direction. Force applied by oar and water are of equal magnitude but in opposite directions. |
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| 265. |
A cricket ball of mass’m’ is thrown upward with some initial speed. If the air resistance is neglected, what forces are acting on the ball when it reaches (a) half its maximum height and (b) its maximum height? |
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Answer» The forces which are acting on the ball thrown vertically upward: a) At half of its maximum height: 1. The remaining force which acts vertically upwards (some force that we applied is utilized in reaching half of maximum height). 2. The gravitational force downwards. b) At maximum height: Gravitational force acts downward direction (The applied force is completely utilized in reaching maximum height) |
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| 266. |
In the given diagram, field force isA) fB) T C) F D) W |
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Answer» Correct option is D) W |
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| 267. |
From the given diagram, you may noticed that F pair of forces acting in opposite directions area) Normal force and frictional force b) Normal force and gravitational force c) Frictional force and external force d) Normal force and external force e) Frictional force and gravitational forceA) a, b B) b, c C) c, d D) d, e |
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Answer» Correct option is B) b, c |
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| 268. |
From the given figure, the force which is pulling the cart isA) contact force B) force at a distance C) muscular force D) A and C |
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Answer» Correct option is D) A and C |
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| 269. |
From this experiment, you can conclude thatA) the surface area is smaller, the pressure will be greater. B) the surface area is greater, the pressure will be greater. C) the surface area is smaller, the pressure remains same. D) none |
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Answer» A) the surface area is smaller, the pressure will be greater. |
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| 270. |
Classify the following as contact and non-contact forces : 1. A horse pulling a cart 2. A magnet attracting a piece of iron. 3. A freely falling stone. 4. A boy shooting an arrow from a bow. 5. Tides in the sea. 6. A speeding car stops when an engine is switched off. 7. Two negatively charged ball repelling each other. 8. Crushing paper into paper ball. |
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Answer» 1. A horse pulling a cart → Contact force. 2. A magnet attracting a piece of iron → Non contact force. 3. A freely falling body → Non-contact force. 4. A boy shooting an arrow from a bow → Contact force. 5. Tides in the sea → Non-contact force. 6. A speeding car stops when an engine is switched off → Contact force. 7. Two negatively charged ball repelling each other → Non-contact force. 8. Crushing paper into paper ball → Contact force. |
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| 271. |
What are contact forces? Give four examples of contact forces. |
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Answer» Contact forces : “The forces which act on another body through some connector are called contact forces.” Or “The forces which act on bodies when they are in actual contact.” Examples : 1. Force of friction 2. Force of tension. 3. A player can set a ball in motion by hitting it with his foot or by pushing it with a bat. 4. Pulling a rubber bond to increase its length. |
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| 272. |
An archer shoots an arrow in the air horizontally. However, after moving some distance, the arrow falls to the ground. Name the initial force that sets the arrow in motion. Explain why the arrow ultimately falls down. |
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Answer» The archer stretches the string of the bow by applying muscular force. In the process the shape of the bow changes. When the string is released, it regains its original position that provides the initial force to set the arrow in motion. The force of gravity that acts on the arrow in the downward direction brings it to the ground. |
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| 273. |
Match the followinga) Changes the speed of an objecti) hitting a ball projected by a bowlerb) Changes the shape of an objectii) making a ship with a paperc) Changes the direction of an objectiii) applying brakes for a moving carA) a – iii, b – ii, c – i B) a – i, b – ii, c – iii C) a – iii, b – i, c – ii D) a – ii, b – i, c – iii |
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Answer» A) a – iii, b – ii, c – i |
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| 274. |
Which of the following is a correct statement? A) A car is in rest, no forces acting on it. B) A car is in rest, net force acting on it is zero. C) A car is in non-uniform motion, net force acting on it is zero. D) None |
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Answer» B) A car is in rest, net force acting on it is zero. |
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| 275. |
Fig. 11.8 shows a car sticking to an electromagnet. Name the forces acting on the car? Which one of them is larger? |
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Answer» Magnetic force (in the upward direction) and force of gravity or the weight of the car (downward). Magnetic force is larger than the force of gravity. |
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| 276. |
What are the various effects of force ? State one example of each. |
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Answer» Various effects of force : 1. A force can move a stationary object. Example : Pulling a suitcase on its wheels. 2. A force can stop a moving object. Example : A ball rolling on rough surface comes to rest after some time due to force of friction. 3. A force can change the speed of a moving object. Example: We can increase the speed of a moving swing, we apply a force (push) in the direction of motion to increase its speed. 4. A force can change the direction of a moving object. Example: A moving bicycle changes its direction when a force is applied to steer its handle. 5. A force can change the shape and size of an object. Example: When we make a chapatti, a small ball of dough is changed to a flat, circular shape of a much bigger size by applying a force with the help of a rolling pin. |
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| 277. |
How can you differentiate between a contact force and a force at a distance? (OR) Distinguish between a contact force and a force at a distance. |
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Answer»
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| 278. |
We can differentiate ‘contact force’ and ‘field force’ by A) magnitude B) direction C) distance of contact D) above all |
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Answer» C) distance of contact |
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| 279. |
A spanner (or wrench) has a long handle. Why? |
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Answer» A spanner (or wrench) has a long handle to produce larger turning moment so that nut can easily be turned with a less force. |
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| 280. |
Define weight. |
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Answer» The gravitational force acting on an object is called the weight of the object. |
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| 281. |
Which of the following is not an effect of force ? 1. Change in the direction of an object 2. Change in the shape and size of an object 3. Change in the mass of an object 4. Change in the position of a stationary object. |
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Answer» 3. Change in the mass of an object |
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| 282. |
Which of the following is a contact force ? 1. Graviational force 2. Frictional force 3. Electrostatic force 4. Magnetic force |
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Answer» 2. Frictional force |
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| 283. |
Friction produces 1. heat 2. change of state 3. electricity 4. pressure |
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Answer» Friction produces heat . |
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| 284. |
Friction for an object can be reduced by 1. providing wheels 2. lubricating 3. streamlining 4. all of these |
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Answer» 4. all of these |
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| 285. |
A truck accelerates from speed v to 2v. Work done during this isA. three times as the work done in accelerating it form rest to vB. same as the work done in accelerating it form rest to vC. four times as the work done in acceleration it from rest to vD. less than the work done in acclerating it from rest to v |
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Answer» Correct Answer - A Work done to accelerate from 0 to v is, `W_(1)=1/2 mv^(2)` Work done to accelerate from v to 2v is, `W_(2)=1/2 m (2v)^(2)` `implies Delta W=W_(2)-W_(1)=1/2 m (2v)^(2) -1/2 mv^(2)=4 W_(1)-W_(1)=3 W_(1)` |
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| 286. |
Explain why a person may bleed from the nose when at a great height above the sea level? |
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Answer» The pressure exerted by the blood in blood capillaries is slightly more than the atmospheric pressure and acts in a direction opposite to that of the atmospheric pressure. Atmospheric pressure decreases with height and at a great height above the sea level, it is very low. As a result, there arises a difference in the internal and external pressures on the walls of the cells and blood capillaries. If the difference is large, it may cause the cell wall and the blood capillaries to burst. Thus, the capillaries in the nose (and ear) may burst causing bleeding. |
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| 287. |
Prove the force = mass x acceleration. State the condition when it holds. |
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Answer» The rate of change of momentum = Δp/Δt = Δ(mv)/Δt (When vc or m is not constant). But if mass m is constant i.e., v<c rate of change of momentum = Δp/Δt = m Δv/Δt Here the quantity Δv/Δt= rate of change of velocity i.e., acceleration a. Rate of change in momentum = Δp/Δt= m Δp/Δt = ma Thus, by Newton's second law of motion, F ∝ ma or, F= k ma Where k is a constant of proportionality which can be made equal to 1 by choosing the suitable unit for force. Hence, F = ma when mass m of the body is constant at velocity v which is much smaller than the velocity of light. |
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| 288. |
Name the S.I. unit of (a) momentum, (b) rate of change in momentum. |
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Answer» S.I unit of (a) momentum is kg m s-1 (b) rate of change in momentum is newton(N). |
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| 289. |
A rocket is moving at a constant speed in space by burning its fuel and ejecting out the burnt gases through a nozzle. Answer the following:(a) Is there any change in the momentum of the rocket? If yes, what causes the change in momentum?(b) Is there any force acting on the rocket? If yes, how much? |
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Answer» (a) Yes, there is a change in momentum of the rocket. Decrease in mass of the rocket causes the change in momentum. (b) Yes, there is force acting on the rocket which is equal to the rate of change in momentum. |
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| 290. |
State Newton’s third law of motion. |
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Answer» Third law of motion states that –To every action, there is always an equal and opposite reaction. |
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| 291. |
Define normal force. |
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Answer» The force that a solid surface exerts on any object in the normal direction is called normal force |
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| 292. |
Name and define the S.I. and C.G.S. unit of force. How are they related? |
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Answer» S.I. unit of force is Newton (N). One Newton is that force which when acting on a body of mass 1kg, produces an acceleration of 1 m s-2 in it. C.G.S. unit of force is dyne. One dyne is that force which when acting on a body of mass 1 gram, produces an acceleration of 1 cm s-2 in it. 1 Newton = 105 dyne |
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| 293. |
What is a magnetic force? |
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Answer» The force exerted by a magnet on another magnet. |
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| 294. |
What is a gravitational force? |
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Answer» The attractive forces between any two massive objects is called gravitational force. |
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| 295. |
Define newton (the S.I. unit of force). |
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Answer» S.I unit of force is newton (N). One Newton is that force which when acting on a body of mass 1kg, produces an acceleration of 1 m s-2 in it. |
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| 296. |
Define 1 kgf how is it related to newton? |
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Answer» One kilogram force is the force by which the Earth pulls a mass of 1 kilogram towards itself. 1 kgf = 9.8 N |
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| 297. |
Two identical bars, one which is steel and the other a magnet, are painted with the same colour. How can you tell which one is the magnet using only these two bars? (don’t break the bars) |
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Answer» The bar which attracts the other bar is magnet. The other bar is magnetic material that is steel. |
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| 298. |
Match the following :Column 'A'Column 'B'1. An ox pulling a carta. Magnetic force2. Lifting heavy iron object with a craneb. Electrostatic force3. Weighing with a spring balancec. Muscular force4. Applying brakes to a bicycle.d. Gravitational force5. Picking up pieces of paper with a plastic scale.e. Frictional force |
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| 299. |
Explain what is understood by the following statement: 1 kilogram force (kgf) = 9.8 newton’ |
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Answer» One kilogram force is the force by which the Earth pulls a mass of 1 kilogram towards itself. 1 kgf = 9.8 N |
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| 300. |
An object falling from a tall building …………. . |
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Answer» Gravitational force. |
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