Physics : Work, Energy and Power

The kinetic energy of a body becomes four times its initial value. The new linear momentum will be

• same as the initial value

• four times the initial value

• twice of the initial value

• eight times of the initial value

Maximum energy transfer for an elastic collision will occur if one body is at rest when

• m₁ = m₂

• m₂ = $\frac{1}{2}$m₁

• m₁ >>  m₂

• m₂ >> m₁

Which of the following is path dependent?

• U

• PdV

• P

• V

Two particles are seen to collide and move jointly together after the collision. During such a collision, for the total system.

• both the mechanical energy and the linear momentum are conserved

• linear momentum is conserved but not the mechanical energy

• neither the mechanical energy nor the linear momentum is conserved

• mechanical energy is conserved but not the linear momentum

A body weighed 250 N on the surface assuming the earth to be a sphere of uniform mass density, how much would it weigh halfway down to the centre of the earth?

• 195 N

• 240 N

• 125 N

• 210 N

Assertion:  Centripetal force does no work. 

Reason:  Force and displacement are perpendicular to each other.

• If both assertion and  reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If assertion is false but reason is true.

A wire suspended vertically from one of its ends is stretched by attaching a weight of 200 N to the lower end. The weight stretches the wire by 1 mm. Then the elastic energy stored in the wire is

• 20 J

• 0.1 J

• 0.2 J

• 10 J

Two springs of force constant 1000 N/m and 2000 N/m are stretched by same, force. The ratio of their respective potential energies is

• 2 : 1

• 1 : 2

• 4 : 1

• 1 : 4

A particle rests on the top of a hemisphere of radius R. Find the smallest horizontal velocity that must be imparted to the particle, if it is to leave the hemisphere without sliding down it.

• $\sqrt{\mathrm{gR}}$

• $\sqrt{2\mathrm{gR}}$

• $\sqrt{3\mathrm{gR}}$

• $\sqrt{5\mathrm{gR}}$

Two bodies A and B have masses M and m respectively, where M > m and they are at a distance d apart. Equal force is applied to them so that they approach each other. The position where they hit each other is

• nearer to B

• nearer to A

• at equal distance from A and B

• Cannot be predicted