Physics : Work, Energy and Power

Which of the following is not an inelastic collision ?

• A man jump on a cart

• A bullet embedded in a block

• Collision of two glass ball

• none of the above

A force F acting on an object varies with distance x as shown here. The force is in newton and distance is in metre. The work done by the force in moving the object from x = 0 to x = 6 m is

• 4.5 J

• 13.5 J

• 9.0

• 18.0 J

A 5 A fuse wire can withstand a maximum power of 1 W in circuit. The resistance of the fuse wire is

• 0.2 Ω

• 5 Ω

• 0.4 Ω

• 0.04 Ω

A particle of mass 100 g is thrown vertically upwards with a speed of 5 m/s. The work done by the force of gravity during the time the particle goes up is

• -0.5 J

• -1.25 J

• 1.25 J

• 0.5 J

A mass of M kg is suspended by a weightless string. The horizontal force that is required to displace it until the string makes an angle of 45° with the initial vertical direction is

• $\mathrm{Mg} \left(\sqrt{2} + 1\right)$

• $\mathrm{Mg} \sqrt{2}$

• $\frac{\mathrm{Mg}}{\sqrt{2}}$

• $\mathrm{Mg} \left(\sqrt{2} -1\right)$

An alpha nucleus of energy $\frac{1}{2} {\mathrm{mv}}^2$ bombards a heavy nuclear target of charge Ze. Then the distance of closest approach for the alpha nucleus will be proportional to

• v²

• 1/ m

• 1/ν⁴

• 1/ Ze

For inelastic collision between two spherical rigid bodies

• the total kinetic energy is conserved

• the total mechanical energy is not conserved

• the linear momentum is not conserved

• the linear momentum is conserved

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