1. LESSON OBJECTIVE Practise Newton’s 2 nd law A car is using a tow bar to pull a trailer along a straight, level road. There are resisting forces R acting on the car and S acting on the trailer. The driving force of the car is D and its braking force is B. Draw diagrams to show the horizontal forces acting on the car and the trailer: i) When the car is moving at a constant speed ii) When the speed of the car is increasing iii) When the speed of the car is decreasing

2. A car of mass 1000 kg tows a caravan of mass 750 kg along a horizontal road. The engine of the car exerts a forward force of 2500 N. The resistances to the motion of the car and caravan are each k × their masses, where k is a constant. Given that the car accelerates at 1ms -2, find the tension in the tow-bar.

3. A stationary helicopter is raising two people of masses 90kg and 70kg as shown. a) Draw a diagram to show all the forces acting on the people (ignore the forces acting on the helicopter) b) When the force applied to the 90kg is 1800 N find the acceleration of both people and the tension in the ropes. Take g = 10ms -2

4. A block A of mass 100kg is suspended by a vertical cable. A block B of mass 150 kg is suspended from block A by another vertical cable. The blocks are raised 10 metres in 10 seconds with a constant acceleration. Find the tension in each cable. 1 3

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