Physics : Work, Energy and Power

Assertion:  Power of a engine depends on mass, angular speed, torque and angular momentum, then the formula of power is not derived with the help of dimensional method. 

Reason:  In mechanics, if a particular quantity depends on more than three quantities, then we can not derive the formula of the quantity by the help of dimensional method.

• 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 both assertion and reason are false.

A gun of mass 10 kg fires 4 bullets per second. The mass of each bullet is 20 g and the velocity of the bullet when it leaves the gun is 300 m s^-1. The force required to hold the gun when firing is

• 6 N

• 8 N

• 24 N

• 240 N

A stone of mass 0.3 kg attached to a 1.5 m long string is whirled around in a horizontal circle at a speed of 6 m s^-1 The tension in the string is

• 10 N

• 20 N

• 7.2 N

• 30 N

If the linear momentum is increased by 50%, then kinetic energy will increase by

• 0 %

• 100 %

• 125 %

• 25 %

A body moves from rest with a constant acceleration. Which one of the following graphs represents the variation of its kinetic energy K with the distance travelled (x)?

Consider the system shown in figure. The pulley and the string are light and all the surfaces are frictionless. The tension in the string is (take g = 10 ms^-2)

• 0 N

• 1 N

• 2 N

• 5 N

Assertion:  Heavy water is used as moderator in nuclear reactor.

Reason:  Water cool down the fast neutron

• 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 both assertion and reason are false.

Assertion:  KE is conserved at every instant of elastic collision. 

Reason:  No deformation of matter occurs in
elastic collision.

• 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 both assertion and reason are false.

A mass M is tied to the top of two identical poles of height H using massless strings of equal length. The mass is at height h above the ground at equilibrium. If the distance between poles is L the tension in each string will be

• $\frac{\mathrm{Mg} \sqrt{{\left({\displaystyle \frac{\mathrm{L}}{2}}\right)}^2 + {\left( \mathrm{H} - \mathrm{h} \right)}^2}}{2 \left(\mathrm{H} - \mathrm{h}\right)}$

• $\frac{\mathrm{Mg} \sqrt{{\mathrm{L}}^2 + {\mathrm{H}}^2}}{2 \left(\mathrm{H} - \mathrm{h}\right)}$

• $\frac{\mathrm{Mg} \sqrt{{\mathrm{L}}^2 + {\mathrm{H}}^2}}{2 \mathrm{H}}$

• $\frac{\mathrm{Mg} \sqrt{{\mathrm{h}}^2 + {\mathrm{L}}^2}}{2 \mathrm{L}}$

A body is moved in straight line by machine with constant power. The distance travelled by it in time duration t is proportional to

• t^3/2

• t^1/2

• t²

• t