college physics help

Question

anonymous · Answer

Two crates of mass 65 kg and 125 kg respectively are at rest on a horizontal surface and touching each other; the kinetic friction coefficient between crates and surface is 0.18. A 650 N force is exerted on the 65 kg crate. (a) Calculate the acceleration of the system and the force the crates exert on each other. (b) Calculate the same quantities if you push with the same force into the 125 kg crate.

anonymous · Answer

In order to solve this problem, we first need to calculate the normal forces of our crates, so that we can calculate the force of friction resisting their motion. This is $$F_f = \mu F_N = \mu mg$$Now using Newton's second law, we know that $$F = ma$$To solve for the acceleration of our system, we need to solve the equation $$650 - F_f = ma$$Using the value for the force of friction we calculated earlier, we can solve for the acceleration of our system. 

Remember, from Newton's third law, for every force, there is an equal an opposite force. In order to solve for the force that the first box exerts on the second box, you need to solve for the force that the first box is exerting on the second box. This is done by solving the equation $$F = m_1a$$where m1 is the first box that is being pushed, and a is the acceleration that was calculated in the first part.