forces – friction

1. The problem statement, all variables and given/known data

A man is pulling a 40.0 kg crate across a level floor with a horizontal force, and the coefficient of kinetic friction is μk = 0.59 for the crate and the floor.

14. What is the normal force acting on the box?
a) 231 N
b) 340 N
c) 196 N
d) 392 N

15. What horizontal force must the man apply to get the crate to accelerate at 2.0 m/s2 ?
a) 311 N
b) 231 N
c) 81 N
d) 40 N

2. The attempt at a solution

For 14:
N = mg = (40.0)(9.8) = 392N

For 15:
N-Fx = max
392 – Fx = (40.0)(2.0)
Fx = 312N

but there’s no 312N there and I didn’t even incorporate the μk?

http://ift.tt/1hX7Joj

Leave a comment

Your email address will not be published.


*


Show Buttons
Hide Buttons