Question 9

A car pulls a trailer with a force of 150 N.

(a) According to Newton’s third law, forces exist in pairs.

(i) What is the other force that makes up the pair? [1]
(ii) Write down the size and direction of this force. [1]

(b) The mass of the trailer is 190 kg. As it sets off from rest, there is a resistive force of 20 N.

(i) Calculate the size and direction of the resultant force on the trailer. [1]
(ii) Calculate the initial acceleration of the trailer. [3]

(c) The force from the car on the trailer is maintained at 150 N.

When the car and trailer are travelling at constant speed:
(i) what is the size of the resultant force on the trailer? [1]
(ii) write down the size and direction of the resistive force on the trailer. [1]

Southampton University
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