Work, Energy and Power

300 J of work is done in sliding a 2 kg block up an inclined plane of height 10 m. Taking g =10 m/s², work done against friction is

• 200J

• 100 J

• zero

• 1000 J

A motor cycle is going on an overbridge of radius R. The driver maintains a constant speed. As the motor cycle is ascending on the overbridge, the normal force on it

• increases

• decreases

• remains the same

• fluctuates erratically

If we throw a body upwards with velocity of 4 m/s, at what height does its kinetic energy reduce to half of the initial value? ( Take g = 10 ms^-1 )

• 4 m

• 2 m

• 1m

• 0.4 m

Two spherical bodies of masses M and SM and radii R and 2R respectively are released in free space with initial separation between their centres equal to 12 R. If they attract each other due to gravitational force only, then the distance covered by the smaller body just before collision,

• 1.5 R

• 2.5 R

• 4.5 R

• 7.5 R

A ball of mass 2 kg moving with velocity 3 m/s collides with spring of natural length 2 m and force constant 144 N/m. What will be length of compressed spring?

• 2 m

• 1.5 m

• 1 m

• 0.5 m

The work done by a force acting on a body is as shown in the graph. The total work done in covering an initial distance of 20 m is

• 225 J

• 200 J

• 400 J

• 175 J

A body of mass m₁ = 4 kg moves at 5 i  m/s and another body of mass m₂ = 2 kg moves at 10 i  m/s. The kinetic energy of centre of mass is

• $\frac{200}{3}\mathrm{J}$

• $\frac{500}{3} \mathrm{J}$

• $\frac{400}{3}\mathrm{J}$

• $\frac{800}{3}\mathrm{J}$

The potential energy of a body is given by U = A - Bx² (where x is the displacement ) The magnitude of force acting on the particle is

• constant

• proportional to x

• proportional to x²

• inversely proportional to x

A gas expands 0.25 m³ at constant pressure 10³ N/m², the work done is

• 250 N

• 250 W

• 250 J

• 2.5 erg

A ball is released from certain height which losses 50% of its kinetic energy on striking the ground it will contain a height again

• $\frac{1}{4}\mathrm{th}$ of initial height

• $\frac{1}{2}\mathrm{th}$ of initial height

• $\frac{3}{4}$th of initial height

• None of the above