11.

Assertion: A particle strikes head-on with another stationary particle such that the first particle comes to rest after collision. The collision should necessarily be elastic.

Reason: In elastic collision, there is a loss of momentum ofthe system of the particles.

• 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:  Pseudo force is an imaginary force which is recognised only by a non-inertial observer to explain the physical situation according to Newton's laws.

Reason: Pseudo force has no physical origin, i.e., it is not caused by one of the basic interactions in nature. It does not exist in the action-reaction pair.

• 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: Work done in moving a body over a closed loop is zero for every force in nature.

Reason: Work done does not depend on nature of force.

• 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:  Two bodies of masses M and m (M > m) are allowed to fall from the same height if the air resistance for each be the same then both the bodies will reach the earth simultaneously. 

Reason:  For same air resistance, acceleration of both the bodies will be same.

• 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: Kepler's second law can be understood by conservation of angular momentum principle.

Reason:  Kepler's second law is related with areal velocity which can further be proved to be based on conservation of angular momentum as (dA/dt) = ( r²ω / 2 )

• 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:  A solid sphere is rolling on a rough horizontal surface. Acceleration of contact point is zero. 

Reason:  A solid sphere can roll on the smooth surface.

• 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:  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 body initially at 80°C cools to 64°C in 5 min and to 52°C in 10 min. The temperature of the surrounding is

• 26^oC

• 16^oC

• 36^oC

• 40^oC

A wave packet with center frequency ω is propagating in dispersive medium with phase velocity of 1.5 x 10³ m/s. When the frequency ω is increased by 2%, the phase velocity is found to decrease by 3 %. What is group velocity of the wave packet?

• 0.25 × 10³ m/s

• 1.0 × 10³ m/s

• 0.6 × 10³ m/s

• 0.75 × 10³ m/s

A solid sphere of volume V and density p floats at the interface of two immiscible liquids of densities and p, respectively. If ρ₁ < ρ < ρ₂, then the ratio of volume of the parts of the sphere in upper and lower liquid is

• $\frac{\mathrm{\rho } - {\mathrm{\rho }}_1}{{\mathrm{\rho }}_2 - \mathrm{\rho }}$

• $\frac{{\mathrm{\rho }}_2 - \mathrm{\rho }}{\mathrm{\rho } - {\mathrm{\rho }}_1}$

• $\frac{\mathrm{\rho } + {\mathrm{\rho }}_1}{\mathrm{\rho } + {\mathrm{\rho }}_2}$

• $\frac{\mathrm{\rho } + {\mathrm{\rho }}_2}{\mathrm{\rho } + {\mathrm{\rho }}_1}$