Work, Energy and Power

If the heat of 110 J is added to a gaseous system, whose internal energy is 40 J, then the amount of external work done is

• 180J

• 70J

• 110J

• 30J

Amount of work which can be obtained from 200 cal heat, will be

• 280 J

• 800 J

• 420 J

• 840 J

The spring extends by x on loading, then energy stored by the spring is (if T is the tension in spring and k is
spring constant

• $\frac{{\mathrm{T}}^2}{2\mathrm{k}}$

• $\frac{{\mathrm{T}}^2}{2{\mathrm{k}}^2}$

• $\frac{2k}{{\mathrm{T}}^2}$

• $\frac{2{\mathrm{T}}^2}{k}$

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