A particle starts its motion from rest under the action of a constant force. If the distance covered in first 10 seconds is S₁ and that covered in the first 20 seconds is S₂, then

A particle moves in a straight line with a constant acceleration. It changes its velocity from 10 ms^$$-$$1 to 20 ms^$$-$$1 while passing through a distance 135 m in t second. The value of t is

The distance travelled by a particle starting from rest and moving with an acceleration $${4 \over 3}$$m s^$$-$$2, in the third second is

A car moves from X to Y with a uniform speed v_u and returns to Y with a uniform speed v_d. The average speed for this round trip is