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KINETIC FRICTION You’re trying to move a large, 60kg wooden crate across a wooden floor. (μs...

KINETIC FRICTION

You’re trying to move a large, 60kg wooden crate across a wooden floor. (μs = 0.35). YoYou try again pushing with 120N perfectly horizontally. Again you realize you can exploit the relationship between normal force and friction to make your life easier, and decide to attach a rope and drag the box, pulling up with at an angle of 10°. You easily match the former acceleration of 0.04 m/s2 .

A. Draw a free-body diagram for the box.

B. Write Newton’s second law for the x-direction and for the y-direction.

C. What is the new, smaller force you’re pulling with now? Note: For this problem, it is helpful to re-write the pulling force components in terms of magnitude and angle, like I did for the first example. You’ll have to do some substituting of one dimension’s equation into the other.

Answer: 118N

Solutions

Expert Solution

(A) The free body diagram for the box is given below.

(B) According to Newton's second law, the net force in the x-direction is

The net force in the y direction is

(C) In the question it is said that the body has same acceleration of 0.04m/s2 when a force of 120N was used and when rope was used.

If is the coefficient of kinetic friction, then the equation when 120N force was used horizontally is

Now when the rope is attached,

The smaller pulling force is 118N

genius_generous answered 1 year ago

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