# A 1200 Kg car pulls an 820 Kg trailer over a rough road. The force of friction acting on the trailer is 650 N.(backwards). Calculate the force that ........the car exerts on the trailer if a). The...

A 1200 Kg car pulls an 820 Kg trailer over a rough road. The force of friction acting on the trailer is 650 N.(backwards). Calculate the force that ....

....the car exerts on the trailer if

a). The trailer is moving at a constant velocity of 30 Km/h.

b). The trailer is moving forward at 60 Km/h and starts accelerating 1.2 m/s^2 (backwards).

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### 1 Answer

We can use Newton's second law of motion for this.

Let;

F = Force that car exerts on trailer

F1 = friction force = 650N

For the first part since it is running with constant velocity there is no acceleration.

`F = ma` to trailer at the direction of cars' motion

`F-F1 = ma`

`F-650 = 820*0`

` F = 650 N`

*So the car exerts 650N force on triler when it travels in constant speed.*

Note:

For the second one you can use the same F = ma

Remember the acceleration is at the backward side or opposite direction of the direction of travel. So you need a negative sign to acceleration component.

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