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Net Force Problems. 1. An airplane has 4 forces acting on it: weight, drag (air friction), the thrust of the engines and the lift force caused by the.

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Presentation on theme: "Net Force Problems. 1. An airplane has 4 forces acting on it: weight, drag (air friction), the thrust of the engines and the lift force caused by the."— Presentation transcript:

1 Net Force Problems

2 1. An airplane has 4 forces acting on it: weight, drag (air friction), the thrust of the engines and the lift force caused by the flow of air over the wings. a. b.5000 N up c.If the pilot wishes the airplane to move forward, then the ______ must be greater than the _______. Airplane F weight F drag F thrust F lift 55,000 N 50,000 N 20,000 N thrust drag

3 2. A 200 N table has a 30 N book resting upon it. a. b. Book 30 N = mass of book x acceleration (9.81 m/s 2 ) 30 N = equal and opposite force of the table pushing up on the book (called the normal force) Fweight of book F table

4 3. A child weighing 150 N is sitting on a swing. The swing is equally supported by 2 ropes, one on each side. What is the force exerted by each rope? a. Each rope must exert a force of 75 N. 150 N = 75 N + 75 N Swing seat F child = 150 N, which is the force of weight due to gravity F rope = 75 N, which is the tension force F rope

5 4. Two chains are used to support a small boat weighing 1500 N. One chain has a tension of 600 N. What is the force exerted by the other chain? a. b.F chain 2 = F weight - F chain 1 = 1500 N – 600 N = 900 N Boat F weight = 1500 N F chain 1 = 600 N F chain 2

6 5. A heavy box weighing 1000 N sits on the floor. You press down on the box with a force of 450 N. What is the normal force on the box? (Same method as #4) A normal force is perpendicular to the plane of action. Box F n = 1450 N F w = 1000 N F p = 450 N

7 6. A 40 N cat stands on a chair. If the normal force on each of the cats back feet is 12 N, what is the normal force on each front foot? (Same method as #4) The normal force must equal the force of the cats weight 40 N = 2(12 N) + 2x 40 N = 24 N + 2x 16 N = 2x 8 N = x Therefore, the normal force on each front foot is 8 N

8 7. Two forces are acting on a pencil, pushing it to the right. One force is 9 N and the other is 6 N. There is a 6 N force pushing the pencil to the left. What is the net force acting on the pencil? (Dont forget the direction!) Pencil F p = 6 N F p = 9 N Pencil F p = 9 N The net force acting on the pencil is 9 Newtons to the right.

9 8. A train is climbing a gradual hill. The weight of the train creates a downhill force of 150,000 N. Friction creates an additional force of 25,000 N acting in the same direction. How much force does the trains engine need to produce so that the train is in equilibrium (not sliding back down the hill)? F t = F f + F w F t = 25,000 N + 150,000 N = 175,000 N Train F w = 150,000 N F f = 25,000 N F t = ? N


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