Physics [2 Mark Question Answer]

Force (F) = 80 N
Perpendicular distance = 1.75 m
∴ Moment of force = F × perpendicular distance
= 80 × 1.75 = 140 Nm.

We know W = F d cos θ.
Since force is normal to displacement.
So θ = 90°
Hence work done W = Fd cos θ 90 = 0.

The forces which act on a body without the help of any connector, are called non-contact forces or forces of distance. Gravitational force, Mechanical force, etc., are non-contact forces.

(i) At Kalpakkam in Tamil Nadu, and
(ii) At Narora, in Uttar Pradesh.

Renewable sources of energy: Solar energy and wind energy.
Non-renewable sources of energy: coal and oil.

The man moving along the slope expends more energy. It is because, while moving along the slope, he gains height and hence has extra potential energy.

In transforming the mechanical energy if a part of it gets converted into another form of energy that cannot be utilized for useful work, this loss of energy is called the dissipation of energy.

The man moving along the slope expends more energy. It is because, while moving along the slope, he gains height and hence has extra potential energy.

The kinetic energy possessed by a moving body is measured by the amount of work done by an opposing force in bringing the body to rest from its present state of motion.

The two conditions are:
(i) Application of-force on the body.
(ii) Displacement of the body in the direction of the force.

Yes, since power = work/time the two agents can have different powers if they take different amounts of time to do the same work.

(i) When there is no displacement by the force in the body.
(ii) When the displacement is normal to the direction of the force.

The weight of a body placed at the centre of the earth is zero as
g = 0
∴ W = mg
= 0

A person going uphill has to bend forward but while coming down has to bent backward, this is to keep the CG at the centre of the body and between his feet.

At each of circular path, the particle, instead of moving straight continuously, turn towards the centre. Therefore, the motion in the circular path is under the action of a force called the centripetal force.

In the MKS system, the unit of the couple is Nm and kgf m.
In the CGS system, the units of the couple are Dyne cm and gf cm.

If the couple has a tendency to rotate the body in an anti-clockwise direction then its moment is taken positive and if the tendency of rotation is clockwise then the moment is negative.

When the number of forces acting on a body, keep it in equilibrium, then the sum total of clockwise moments about any turning point is equal to sum total of anticlockwise moments about the point.

In the CGS system, the unit of moment of a force is Dyne-cm and in the MKS system, the unit of moment of a force is Newton-metre. The gravitational units in CGS and MKS system of measurement are gf cm and kg m respectively.

When force is applied on a non-rigid body it undergoes deformation i.e. change in size, shape, and position whereas a rigid body doesn’t undergo a change in shape, position, and size.

The moon is revolving around the earth. In this process, the work done by the gravitational force is zero because the displacement of the moon is at the right angle to the gravitational force.

Two effects of a force on a non-rigid body are:
(i) Force can change the state of rest or motion of the body
(ii) Force can change the size or shape of the body.

The kinetic energy changes to potential energy when stone rises up. The potential energy then changes back to kinetic energy, when stone comes down.

During loading, the mechanical energy changes to the potential energy of spring. On firing, the potential energy of spring changes to the kinetic energy of the bullet.

The mechanical energy changes to potential energy during winding. The potential energy is then released in the form of kinetic energy.

Work is said to be done only when the applied force on a body makes the body move but power is the rate of doing work.
The SI unit of work is 'joules' and that of power is 'watt'.

Resisting force = 75 N; Distance moved = 30 m
∴ Work done = 75 × 30 J = 2250 J.

(i) Compressed spring possesses potential energy.
(ii) Potential energy of the spring is imparted to the ball in the form of kinetic energy.

Moment of a force about the point O
= Force × Perpendicular distance of force from the point O
= F × OP

(i) Work done in moving the block from = F × d
A to B = 200 N × 3m = 600 J
(ii) Gain in potential energy = mgh = 30 × 10 × 1.5 = 450 J.

(i) A moving bullet
(ii) A flowing river
(iii) Wind.

Mechanical energy is of two forms:
(i) potential energy, and
(ii) kinetic energy.