InterviewSolution
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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.
| 1. |
Calculate the force required to impact a car a velocity of `30m//s`, in 10 seconds. The mass of the car is `1500kg` |
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Answer» Hence, force required,F=?, final velocity, `v=30m//s`, time taken, `t =10 s` initial velocity, u = 0, mass of car, `m = 1500kg` As `F=ma =(m(v-u))/t =(1500(30-0))/10= 4500N` |
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| 2. |
The velocity of a body is doubled. What happens to its momentum? |
| Answer» Momentum would become twice , as `p=mv` | |
| 3. |
A machine gun fires `25g` bullets at the rate 600 bullets per minute with a speed of `400m//s`. Calculate the force required to keep the gun position |
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Answer» Here, `m=25 g = 25xx10^(-3) kg , n=(600)/(60)= 10` bullet/sec, `v=400m//s, F=?` F= rate of chang e of momentum of bullets = n m v `= 10xx25xx10^(-3)xx400=100N` |
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| 4. |
A person manages to push a car of mass `800 kg` with a uniform velocity along a level road. When another person joins him and pushes the car with an equal force, the acceleration produced is `0.5m//s^(2)`. Calculate the force with which each person pushes the car. |
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Answer» Let `F` be the force applied by each person. In the first case, when velocity is uniform, F=f=force of friction. In the second case, applied force `= F+F= 2F` Net force producing acceleration `= 2F-f = 2F-F= m a = 800xx0.5= 400N` |
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| 5. |
What are the units of linear momentum? |
| Answer» `kg ms^(-1)`. | |
| 6. |
Define momentum of a body. |
| Answer» The momentum of a body is the product of mass of the body and velocity of the body. | |
| 7. |
Are the force of action and reaction always equal in magnitude? |
| Answer» Yes, they are. | |
| 8. |
The force of action and reactionA. always cancel eachotherB. never cancleC. cancle sometimesD. can not say |
| Answer» The force of action and reaction never cancel eachother. | |
| 9. |
Why should a gun be held tightly against the shoulder, while firing? |
| Answer» This is necessary to avoid injury to the shoulder on account of recoiling of gun. | |
| 10. |
A body of mass `5kg` is moving along a circle of a radius `1 m` with a uniform speed of 5 `m/s`.What is the acceleration of body? |
| Answer» Centripetal acc, `a=(v^(2))/r= (5xx5)/1= 25 m//s^(2)`. | |
| 11. |
What force is required to move a body of mass `1kg` with a uniform velocity of `1m//s`? |
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Answer» As velocity is uniform acceleration `a=0` `:.` F=ma=zero, i.e., no force is required. |
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| 12. |
A body of mass `5kg` is moving along a circle of radius `1m` with a uniform speed of `5m//s`. The external force acting on the body is |
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Answer» For uniform circular motion, force required `F=(mv^(2))/r= (5xx5^(2))/1= 125N` |
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| 13. |
A body of mass `1kg` is moving along a straight line with a velocity of `1m//s`. The external force acting in the body isA. `1N`B. 1 dyneC. `1J`D. zero |
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Answer» Correct Answer - D As acceleration `=0, F= ma = zero. |
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| 14. |
An object of mass `100kg` is accelerated uniformly from a velocity of `5m//s` to `8m//s` in `6 s`. Calculate the initial and final momentum of the object. Also, find the magnitude of the exerted on the object. |
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Answer» Here, `m=100kg, u=5m//s, v=8m//s, t=6 s ` Initial momentum of object, `p_(1)= m u=100xx5=500 kg m//s` final momentum of object, `p_(2)=mv=100xx8=800kg m//s` Force exerted, `F = ("change in momentum")/("time taken")=(p_(2)-p_(1))/t=(800-500)/6=50N` |
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| 15. |
A body of mass `1kg` is moving with a uniform speed of `1m//s` in a circular path of radius `1m`. The external force acting on the body isA. `1N`B. 1 dyneC. `1J`D. zero |
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Answer» Correct Answer - A `F=(mv^(2))/r= (1xx1^(2))/1= 1N` |
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| 16. |
When two bodies `A` and `B` interact with each other, A exerts a force of `10N` on `B`, towards east. What is the force exerted by `B` on `A`? |
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Answer» Here, force exerted by A on B `= F_(AB)=10N` (towards east) force exerted by B on A ` =F_(BA)=?` As `F_(BA)= -F_(AB), F_(BA)= -10N`,i.e., B exerts `10N` force on A towards west. |
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| 17. |
Which of the following statement is not correct for an object moving along a straight path in an accelerated motion?A. Its speed keep changingB. Its velocity always changesC. It always goes away from the earthD. A force is always acting it |
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Answer» Correct Answer - C An object moving along a straight path in an accelerated motion may not always go away from earth. It may also be moving towards the earth. |
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| 18. |
Can balanced forces stop a mooving body? |
| Answer» Answer is No | |
| 19. |
(a)Which forces- balanced or unbalanced can change the state of a body? (b)what is measure of inertia of a body in linear motion? |
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Answer» (a)Unbalanced force alone can change the state of a body. (b)Mass of a body is measure of inertia of the body in linear motion. |
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| 20. |
Can balanced forces change the shape and size of a body? |
| Answer» Yes they can. | |
| 21. |
What are balanced forces? |
| Answer» If the resultant of all the forces acting on a body is zero, the forces are called balanced forces. | |
| 22. |
Name the property of bodies due to which they resist change in their state of rest or state of uniform motion along a straight line. |
| Answer» This is the property of inertia. | |
| 23. |
Can balanced forces move a body at rest? |
| Answer» Answer is No | |
| 24. |
A body at rest oppose the forces which try to move it. What is this property called? Give at least one example. |
| Answer» This property is called inertia of rest. For example, when a bus starts suddenly, the passenger has a tendency to fall backwards. This is because lower portion of his body moves with the bus and upper part of his body tends to remain at rest. | |
| 25. |
A body at rest continues to be at rest underless some external force force is applied to move it. Rather, the body at rest opposes the force that tends to move it. Left to itself, the body at rest, will never start moving. This is well known property of inertia of rest of bodies, we study in Physics. ltRead carefully the above passage and answer the following questions: (i) When a bus start moving suddenly, the passengers tend to fall backward. Why? (ii) Give one more example of inertia of rest. (iii) What values do you inculcate in life from this study? |
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Answer» (i) The passenger tend to fall backward, because of the property of inertia of rest. The lower part of the body in contact with the seat moves with the bus. The upper part of the body tends to remain at rest. That is why the passenger tend to fall backwards. When a branch of tree laden with mangoes is shaken vigorously, some of the mangoes fall down. This is due to inertia of rest of the mangoes. (iii) In a day to day life, we find that the law of inertia is applicable universally. For example, if I have some bad habit, it will not go on its own. I have to put in efforts to change the same. To start with, I will rather resist myself to adopt the change. Some sort of force in the form of motivation(internal or external) is essentially required to affect the change. The same is true for parents and teachers handling young kids. |
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| 26. |
Using second law of motion, derive the relation between force and acceleration. A bullet of `10g` strikes a sand-bag at a speed of `10^(3)ms^(-1)` and gets embedded after travelling `5cm`.Calculate (i) the resistive force exerted by the sand on the bullet (ii) the time taken by the bullet to come to rest. |
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Answer» The required relation is `F=ma` Mass of bullet, `m=10g=10^(-2)kg` speed of bullet, `v=10^(3)ms^(-1)` distance travelled, `s=5cm=5xx10^(-2)m` As work done= `K.E` bullet `:. Fxxs=1/2mv^(2)` `F=(mv^(2))/(2s)=(10^(-2)(10^(3))^(2))/(2xx5xx10^(-2))=10^(5)N` From `v=u+at` `0=10^(3)+((-10^(5))/(10^(-2)))xxt, t=10^(3)/(10^(7))=10^(-4)s` |
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| 27. |
The rate of change of ……..of a body……is ………Proportional to the ……..applied. Fill in the blanks. |
| Answer» Linear momentum, directly , external force. | |
| 28. |
A cushioned bed or a sand bed is used in the athletic event high jump. Why? |
| Answer» It increases the time of impact. The athlete is saved from injury. | |
| 29. |
When we stops pedalling a bicycle we are riding, the bicycle beigns to slow. This is becauseA. We stop applying forceB. of unbalanced force of friction between the tyres and the roadC. either (a) and (b)D. neither (a) or (b). |
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Answer» Correct Answer - B unbalance force of friction between the tyres and the road slows down the bicycle. |
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| 30. |
Show that `kg-ms^(-1)` and `N-s` represent the same quantity. Which is that quantity? |
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Answer» `kg-ms^(-1)` = mass `xx` velocity=lin ear momentum `N-s=(kg-m//s^(2)xxs= kgxxms^(-1)` = linear momentum |
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| 31. |
Name the physical quantity whose unit is `kg ms^(-1)`. |
| Answer» It is momentum of the body. | |
| 32. |
A bullet thrown with a hand can be stopped eaisly, but it may kill a person when fired from a gun. Why? |
| Answer» When a bullet is fired from a gun, its velocity is very large compared to when it is thrown with a hand. When velocity is large, its liner momentum is large. Therefore, it may pierce through the person and kill him. | |
| 33. |
A body of mass `30kg` has a momentum of `150kg m//s`. What is the velocity? |
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Answer» Here, `m=30kg, p=150kg m//s, v=?` From `p=mv, v=p/m=(150)/(30)=5m//s`. |
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| 34. |
A ball is thrown vertically upwards. What is its momentum at the highest point? |
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Answer» At the highest point velocity, `v=0` Thus, `p=mv=Zero`. |
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| 35. |
Inertia of a body in linear motion is measured by itsA. velocityB. momentumC. massD. none of the above. |
| Answer» Mass of a body is a measure of inertia of the body in linear motion. | |
| 36. |
Name the three types of inertia. |
| Answer» (i) Inertia of rest (ii) Inertia of motion (iii)Inertia of direction. | |
| 37. |
On what factor does inertia of a body depend? |
| Answer» Inertia of a body depends on mass of body. | |
| 38. |
In Ques.7, acceleration of the body isA. `1m//s`B. `1m//s^(2)`C. `1m`D. zero |
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Answer» Correct Answer - B acc.`=(v^(2))/r= (1xx1)/1= 1m//s^(2)` |
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| 39. |
A gun recoils on firing. This is due toA. force of reaction exerted by the bullet on the gunB. force exerted by the gun on the bulletC. either (a) and (b)D. neither (a) or (b). |
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Answer» Correct Answer - A The recoiling of a gun on firing is due to force of reaction exerted by the bullet on the gun. |
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| 40. |
A swimmer swims due toA. forward push of water on the swimmerB. buoyancy of waterC. either (a) and (b)D. neither (a) or (b). |
| Answer» Swimming is due to forward push of water on the swimmer. | |
| 41. |
Impulse of a force measures the effect of the force. It is the product of force `(F)` and time `(t)` for which the force acts. Mathematically, impulse `=Fxxt`. It is equal to change in linear momentum of the body. For a given change in linear momentum, `Fxxt=constant`. If `t` increases, `F` decreases and vice-versa. For example, a player lowers his hands while catching a cricket ball. This would be increase `t` the time of catch. Therefore, `F` would reduce, i.e., his hands will not get hurt badly. Read the above passage and answer the following questions: (i)Why is crockery wrapped in straw or papers etc.? (ii) Why are vehicles like scooter, car, bus, trucks provided with shockers? (iii)What message does this paragraph give you for your day to day life? |
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Answer» (i) Crockery is wrapped in straw or paper to avoid breakage. In case of mishandling, the impact takes longer time to travel to crockery through straw//papers. As `t` increases, `F` decreases,i.e., impact on crockery reduces, preventing the chance of breakage. (ii)The vehicles like scooter, car,bus, trucks are provided with shockers. When they move over an uneven road, impulsive forces are exerted by road. The function of shokers is to increase the time of impact. This would reduce the force//jerk experienced by the rider of the vehicle. (iii)The message conveyed by the paragraph is that to achieve any goal in life, you have to put in your sincere efforts. More intense are the efforts, lesser will be the time required in achieving the goal. One has to plug all the top holes in the process so that efforts are not wasted. |
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| 42. |
In Ques.8, the direction of acceleration isA. away from the centreB. along the tangent to the circleC. towards the centre and along the radius of the circleD. variable |
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Answer» Correct Answer - C The acceleration is towards the centre and along the radius of the circle. |
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| 43. |
what is the momentum of a man of mass `75kg` when he walks with a velocity of `2m//s`? |
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Answer» Here, `m = 75kg, v=2m//s, p=?` As `p=mv, p= 75xx2=150kg m//s` |
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| 44. |
What is meant by recoiling of a gun? |
| Answer» Recoiling of a gun is moving of the gun backward when the bullet is fired. | |
| 45. |
What would be the force required to produce an acceleration of `2m//s^(2)` in a body of mass `12kg`? What would be the acceleration if the force were doubled? |
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Answer» Here, `F=?,a=2m//s^(2),m=12kg` As `F=ma, F=12xx2= 24N` When force is doubled, acceleration will also be doubled, New acceleration `= 2xx2 = 4m//s^(2)` |
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| 46. |
Suppose a ball of mass `m` is thrown vertically upward with an initial speed `v`, its speed decreases continuously till it becomes zero. Thereafter, the ball beigns to fall downward and attains the speed `v` again before striking the ground. It implies that the magnitude of initial and final momentums of the ball are same. Yet, it is not an example of conservation of momentum. Explain why? |
| Answer» Law of conservation of linear momentum applies only to isolated systems where there is no external force. In this case, change in velocity of ball (upwards and downwards) is due to attractional pull of earth. That is why this motion of ball is not an example of conservation of momentum. | |
| 47. |
Is momentum is scalar or vector? |
| Answer» Momentum is vector quantity. | |
| 48. |
Which physical quantity corresponds to rate of change of momentum? |
| Answer» Answer :- Force. | |
| 49. |
(a)What is meant by an isolated system? (b)Out of mass, speed and momentum, which quantity is same for bullet and the gun on firing? |
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Answer» (a)An isolated system is that on which no external force is acting. (b)Linear momentum of gun is equal and opposite to linear momentum of bullet. |
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| 50. |
A bullet of mass `50g` is fired with an velocity of `150m//s`. If the rifle weights `3kg`. What is its recoil velocity? |
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Answer» Here, `m_(1)=50g= 50xx10^(-3)kg, v_(1)=150 m//s` `m_(2)=3kg, v_(2)=?` As `m_(1)v_(1)+m_(2)v_(2)=0` `:. v_(2)= (-m_(1)v_(1))/(m_(2))= ((50xx10^(-3))xx150)/3=2.5m//s`.momentum of the bullet = Velocity*Mass = 150*0.05 = 7.5 Recoil velocity of the rifle is = momentum of bullet/ mass of gun = 7.5 / 3 =2.5 The recoil velocity of the gun is 2.5 m/s |
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