Question

A 10 kilogram rubber block is pulled horizonitally at constant velocity across a sheet of ice. Calculate the mangitude of the force of friction acting on the block.

A 1,000 kiolgram car traveling due east at 15 meters per second is hit from behind and receives a forward impulse of 6,000 newton-seconds. Determine the magnitude of the car's change in momentum due to this impulse.

Answer 1

as the rubber blocked is pulled a pulling force acts on the block F_p

The force of friction F_f acts opposite to the motion of the block.

The block is moving with const. velocity, hence acceleration =0

and net force on the block =0

F_f = F_p

magnitude of frictional force = magnitude of pulling Force

mass of car m = 1000 kg

               speed = 15 m/s

impulse = 6000 N-s

               = Ft

F = p/t , rate of change of momentum , Newton's second law

change in momentum p = Ft = 6000 kg-m/s