Answer to Question #260192 in Physics for grey tyrant

Question

A car run out of gas on a freeway and needs to be towed by a tow truck with a length of rope. The car has a mass of experiences a normal force of 14,700 N and the coefficient of statistic friction of rubber on cement is 0.85?

a. Draw the free body diagram of the car.

b. How much force does the tow truck have to exert to get the car to start moving?

Answer 1

(a) Let's draw the free body diagram of the car:

(b) In order the car to start moving the following condition must satisfied (the force exerted by the tow truck must overcome the static friction force):

$$F_{tow\ truck}>F_{s.fr.},$$ $$F_{tow\ truck}>\mu_sN$$ $$F_{tow\ truck}>0.85\times14700\ N,$$ $$F_{tow\ truck}>12495\ N.$$

Therefore, to get the car to start moving the force exerted by the tow truck should be greater than 12495 N.