Explore topic-wise InterviewSolutions in .

Correct option is A) No

(1) decreases

(2) friction

(3) gravitational

(4) greater

(5) louder

(6) muscular

When powder is sprinkled on a carrom board,friction between the coin and the board decreases so that the coin can be pocketed easily.

F = m × a 

= 12.5 × 3.5 = 43.75N

mass m = ?

F = 525N a = 3.5m/s²

m = f/a = 525/3.5 = 5250/35 = 150kg

Moment of force = force x perpendicular distance of force from point O

Moment of force = F x r

5Nm = 10 × r

R = 5/10 = 0.5 m

(a) The body will have rotational as well as translational motion.

(a) only rotatory motion

A contact force acts between our hand and tube. So, the toothpaste comes out when we press it.

D) Compass needle moves by magnetic force.

A force at a distance or field force acts on the needle. So, the needle of a magnetic compass moves when we place a bar magnet near it.

When the pile of coin on the carom-board is hit by a striker, coin only at the bottom moves away leaving rest of the pile of coin at same place. This happens because when the pile is struck with a striker, the coin at the bottom comes in motion while rest of the coin in the pile has the tendency to remain in the rest and they vertically falls the carom-board and remain at same place.

1. Tiny pieces of paper get attracted towards the plastic scale or comb

2. Pieces of paper again attracted towards the plastic scale or comb.

Observation : Tiny pieces of paper get attracted towards the plastic scale or comb.

3. When the plastic scale or comp is rubbed with dry hairs it accumulates electrostatic charge. This electrostatically charged scale or comb exerts an electrostatic force on the tiny pieces of paper and thus attracts them.

The object will move in the direction of 5 N force.

(d) electrostatic force

(a) Issac Newton

1. The speed of the ball increases. Observe figure shown below. Conclusion : In figure man is pulling the cart and another person is pushing it from back

2. The speed of the cart increases.

Conclusion : On applying the force in the direction of motion of moving object, its speed increases.

1. Ball starts to rotate and displace from its place. Put a sheet of paper on the table and blow it

2. The position of paper changes.

Conclusion : We observe the leaves and the branches of a tree move because of the force applied by the air. A kick brings a football in motion.

On applying force in the opposite direction of motion of an object its speed decreases.

(c) gravitational force

Two objects must interact with each other for the force to act

Some type of force is applied by the players in these games to change the direction of the ball.

The earth attracts each and every object towards it. So all objects fall toward earth.

Force may 

1. Change the state of an object.

2. Change the speed of an object.

3. Change the direction of motion of an object.

4. Change the shape of an object.

We can push any cart, lift any weight, closer or open the door etc.

We have to apply muscular force.

Either we pull them or push them.

D) normal force

a) Frictional force acting between floor and ball.

b) Contact force and force at a distance. Types of forces:

c) Due to magnetic force of magnet.

d) Due to muscular force applied by us on toothpaste.

e) First one is force at a distance and the second one is contact force.

(a) False

(b) False

(c) True

(d) False

(e) False

(f) True

(g)True

(H) False

(a) Force is applied as push or pull. 

(b) On squeezing a gum tube, its shape changes. 

(c) On pulling a string, its length increases. 

(d) A moving football when kicked, its direction of motion changes. 

(e) On applying brakes on a moving car, its speed slows down. 

(f) We use ball bearings to reduce the friction. 

(g) Friction opposes the motion. 

(h) Lubricants are used to reduce friction. 

(i) Friction causes wear and tear of moving parts of machine.

• Bullet and Gun – When bullet is fired from a gun, gun recoils in the opposite direction of bullet. The momentum of bullet is equal to momentum of gun. Since, the bullet is has very small mass compared to the gun, hence velocity of bullet is very high compared to the recoil of gun. In the case of firing of bullet, law of conservation of momentum is applied as usual.
• When a cricket ball is hit by bat, the Law of Conservation of Momentum is applied.

(d) mv

Mass of the object = m

Velocity = v

Momentum = Mass × Velocity

Momentum = mv

(a) There is an unequal change of distance in an equal interval of time. Thus, the given object is having a non-uniform motion. Since the velocity of the object increases with time, the acceleration is increasing.

(b) According to Newton’s second law of motion, the force acting on an object is directly proportional to the acceleration produced in the object. In the given case, the increasing acceleration of the given object indicates that the force acting on the object is also increasing.

Mass of the dumbbell, m = 10 kg

Distance covered by the dumbbell, s = 80 cm = 0.8 m

Acceleration in the downward direction, a = 10 m/s²

Initial velocity of the dumbbell, u = 0

Final velocity of the dumbbell (when it was about to hit the floor) = v

According to the third equation of motion:

v² = u² + 2as

v² = 0 + 2 (10) 0.8

v = 4 m/s

Hence, the momentum with which the dumbbell hits the floor is

= mv = 10 × 4 = 40 kg m s⁻¹

Yes, it is compulsory that non-contact forces are having both the properties, i.e., attraction and repulsion as both these properties depend on the charge or pole of the object. The object having positive charge will attract a negatively charged object and the same object with positive charge will repel another positively charged object. Thus both attraction and repulsion are there in the same object.

Forces are can also divided into two types:

1. Balanced Forces

2. Unbalanced Forces

1. Balanced Forces:

If the resultant of applied forces is equal to zero, it is called balanced forces.

Example: - In the tug of war if both the teams apply similar magnitude of forces in opposite directions, rope does not move in either side. This happens because of balanced forces in which resultant of applied forces become zero.

Balanced forces do not cause any change of state of an object. Balanced forces are equal in magnitude and opposite in direction.

Balanced forces can change the shape and size of an object. For example - When forces are applied from both sides over a balloon, the size and shape of balloon is changed.

2. Unbalanced Forces:

If the resultant of applied forces are greater than zero the forces are called unbalanced forces.

An object in rest can be moved because of applying balanced forces.

Unbalanced forces can do the following:

• Move a stationary object.
• Increase the speed of a moving object.
• Decrease the speed of a moving object.
• Stop a moving object.
• Change the shape and size of an object.

EFFECT OF FORCE:

1. Force can make a stationary body in motion. For example a football can be set to move by kicking it, i.e. by applying a force.

2. Force can stop a moving body – For example by applying brakes, a running cycle or a running vehicle can be stopped.

3. Force can change the direction of a moving object. For example; By applying force, i.e. by moving handle the direction of a running bicycle can be changed. Similarly by moving steering the direction of a running vehicle is changed.

4. Force can change the speed of a moving body – By accelerating, the speed of a running vehicle can be increased or by applying brakes the speed of a running vehicle can be decreased.

5. Force can change the shape and size of an object. For example -– By hammering, a block of metal can be turned into a thin sheet. By hammering a stone can be broken into pieces.

A force is anything that can cause a change to objects. Forces can:

• change the shape of an object

• move or stop an object

• change the direction of a moving object.

A force can be classified as either a contact force or a non-contact force.

A contact force must touch or be in contact with an object to cause a change. 

Examples of contact forces are:

• the force that is used to push or pull things, like on a door to open or close it

• the force that a sculptor uses to turn clay into a pot

• the force of the wind to turn a windmill

A non-contact force does not have to touch an object to cause a change. 

Examples of non-contact forces are:

• the force due to gravity, like the Earth pulling the Moon towards itself

• the force due to electricity, like a proton and an electron attracting each other

• the force due to magnetism, like a magnet pulling a paper clip towards itself

The unit of force is the Newton (symbol N). This unit is named after Sir Isaac Newton who first defined force. Force is a vector quantity and has a magnitude and a direction.

It is easier to turn the steering wheel of a large diameter than that of a small diameter because less force is applied on steering of large diameter which is at a large distance from the centre of rim.

D) Wringing a wet towel

contact force – 1,4,5

non contact force – 2,3,6

A frictional force acts in the direction opposite to the direction in which the cycle is moving, at the point of contact of wheels with the road.

In a tug of war game, if the two team exert equal forces none of the team wons since it maintain the tug in the equilibrium position or in the same state as the forces are balanced forces.