The frictional force acting on a small block of mass 0.15 kg, while it is moving on a horizontal surface,
has magnitude 0.12 N. The block is set in motion from a point X on the surface, with speed 3 m s−1
. It
hits a vertical wall at a point Y on the surface 2 s later. The block rebounds from the wall and moves
directly towards X before coming to rest at the point Z (see diagram). At the instant that the block
hits the wall it loses 0.072 J of its kinetic energy. The velocity of the block, in the direction from X to
Y, is vm s−1
at time ts after it leaves X.

Question

The frictional force acting on a small block of mass 0.15 kg, while it is moving on a horizontal surface,
has magnitude 0.12 N. The block is set in motion from a point X on the surface, with speed 3 m s−1
. It
hits a vertical wall at a point Y on the surface 2 s later. The block rebounds from the wall and moves
directly towards X before coming to rest at the point Z (see diagram). At the instant that the block
hits the wall it loses 0.072 J of its kinetic energy. The velocity of the block, in the direction from X to
Y, is vm s−1
at time ts after it leaves X.

anonymous · Answer

Perhaps this should be posted in physics section.