Question

A block of mass 4 kg, which has an initial
speed of 2 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.

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/s^2

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

Answer 1

Kinetic energy = (1/2) m v^2
= (1/2)(4)(4)
= 8 joules
so you need 8 Joules to stop it

F = m a
5 = 4 a
a = 5/4 m/s^2 = 1.25 m/s^2

5 x = 8

x = 8/5 = 1.6 meter

Answer 2

First part.
=(1/2)(4)(2)(2)

Answer 3

(1/2)(4)(2)(2) is the same as (1/2)(4)(4)

Answer 4

Woah