Question

Part 1
A block of mass 4 kg, which has an initial
speed of 8 m/s at time t = 0, slides on a
horizontal surface.Find the magnitude of the work that must
be done on the block to bring it to rest.
Answer in units of J.

Part 2
If a constant friction force of magnitude
5 Newtons is exerted on the block by the surface, find the magnitude of the acceleration of
the block.
Answer in units of m/s2.

Part 3
How far does the block slide before it comes
to rest?
Answer in units of m.

Answer 1

1.
enough work must be done to reduce the Ke to zero
so
work = (1/2) m v^2 Joules

2.
a= F/m = 5/4 m/s^2

3.
work done by friction = initial Ke when it stops
5 * d = (1/2) m v^2