Newton's Laws Applications

Question

Suppose you have a 129-kg wooden crate resting on a wood floor. (For each answer, enter a number. 𝜇_k = 0.3 and 𝜇_s = 0.5)

What maximum force (in N) can you exert horizontally on the crate without moving it?

 __N

If you continue to exert this force (in m/s²) once the crate starts to slip, what will the magnitude of its acceleration (in m/s²) then be?

 __m/s²

Answer 1

For first part.

This will be the force of static friction = µ_s mg , where m = mass of crate, g = 9.8 m/s/s

For second part. Net force on crate will be µ_s mg - µ_k mg = mg (µ_s - µ_k). Divide this by m to get the acceleration in m/s/s.