what is the acceleration of the crate?

Question

A crate of mass 105 kg is pulled by a rope on a frictionless surface. The rope makes an angle of 40 ⁰ above the horizontal. If the tension on the string is 938 N, what is the acceleration of the crate?

Answer 1

Because there is no friction, the net force on the crate is simply the horizontal component of the string tension. That 938cos 40 = the 105 kg times its acceleration. So 719 = 105a and a = 6.84 m/s².