Question

I need help on this question.

Answer 1

Answer: B. 49 N

Step-by-step explanation:

Friction Force

When an object is at rest on a rough surface, it encounters a friction force that opposes motion.

The friction force when an object is moving on a horizontal surface is calculated by:

`Fr=\mu_k N`

Where
`\mu_k` is the coefficient of static friction and N is the normal force.

If no forces other then the weight and the normal are acting upon the y-direction, then the weight and the normal are equal in magnitude:

N = W = m.g

Thus, the friction force is:

`Fr=\mu_k W`

We are given the coefficient of static friction
`\mu_k=0.5` and the mass of the object m=10 Kg. The minimum force needed to make it start moving is the maximum friction force:

Fr=0.5*10*9.8

Fr = 49 N

Answer: B. 49 N