Question

A 35 kg box is pulled with a rope from above at an angle of 20. The box begins to move when F 200N. Calculate the frictional force acting on the box. Calculate the normal force acting on the box.

Answer 1

Answer:

b) 188 N

c) 275 N

Explanation:

Draw a free body diagram of the box.  There are four forces:

Applied force F at an angle θ

Weight mg pulling down

Normal force Fn pushing up

Friction force Ff pushing left

(b)

Sum of the forces in the x direction:

∑F = ma

F cos θ − Ff = 0

Ff = F cos θ

Ff = 200 cos 20°

Ff = 188 N

(c)

Sum of the forces in the y direction:

∑F = ma

F sin θ + Fn − mg = 0

Fn = mg − F sin θ

Fn = (35)(9.8) − 200 sin 20°

Fn = 275 N