Question

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Answer 1

Answer:

Answer: B. 49 N

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