Question

(6) A brick, with a mass of 4.0 kg., is placed on a horizontal surface. A

force of 15 N is needed to
push this brick towards the west at a constant velocity.
(a) What is the magnitude of the frictional force? Explain your answer.
(b) What is the magnitude of the normal force? Explain your answer
(c) Determine the value of the coefficient of sliding friction between the
brick and the
surface.

Answer 1

(a) 15 N

(b) 39.2 N

(c) The coefficient of sliding friction is 2.61
`\bar 3`

Step-by-step explanation:

The given parameters are;

The mass of the brick = 4.0 kg

The nature of the surface on which the brick rests = Horizontal

The force needed to move the brick from rest = 15 N

(a) Given that the body is not accelerating, the force applied = The frictional force = 15 N

Which can also be expressed as follows;

The magnitude of the frictional force = The force needed to push the brick to move from rest and move with a constant velocity = 15 N

(b) The magnitude of the normal force = The force acting at right angles to the surface opposite in direction and equal in magnitude to the weight of the brick, so as hold the brick and prevent it from passing through the surface. which is given as follows;

The weight of the block = The magnitude of the normal force =The mass × The acceleration due to gravity = 4.0 × 9.8 = 39.2 N

The magnitude of the normal force = 39.2 N

(c) The frictional force, F =
`\mu _k` × Normal force

Where;

`\mu _k` = The coefficient sliding friction

By substituting the known values gives

15 = μ × 39.2

`\mu _k` = 15/39.2 = 2.61
`\bar 3`.