Answer to Question #161370 in Mechanics | Relativity for Samir khan

Question

A 70.0 kg weight sits at the top of a ramp that makes an angle of 40o with the horizontal. As the weight slides down the ramp, it experiences a force of friction of 75 N. What is the acceleration of the weight down the ramp?

Answer 1

From the Newton's second law:

$ma=mgsin\alpha-F_{fr},$

where m - the mass of a weight;

$\alpha$ - angle, that the ramp makes with the horizontal;

$F_{fr} -$ a force of friction.

Hence,

$a=\frac{mgsin\alpha-F_{fr}}{m}=\frac{70\cdot 9.81\cdot sin40\degree-75}{70}=5.23\space m/s^2.$

Answer: 5.23 $m/s^2.$