Grade 11 forces review PDF

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Test Review - Forces 1. Draw a free body diagram to determine the unbalanced force acting on the underlined object in each of the following situations: a) Two teenagers are pushing a dirt bike through a freshly plowed field. One exerts a force of 400 N [W] on the bike while the other exerts a force of 420 N [W]. Frictional resistance amounts to 810 N. b) A pail of water of mass 8.0 kg falls from the platform of a window washer to the sidewalk below. c) A water skier is being pulled directly behind a motorboat at a constant velocity of 20 m/s. The tension in the horizontal rope is 520 N. d) An elevator, including passengers, has a mass of 1000 kg. The cable attached to the elevator exerts an upward force of 12 000 N. Friction opposing the motion of the elevator is 1500 N. 2. What unbalanced force would be required to accelerate a 0.50 kg grapefruit at a) 4.0 m/s2 ? [2N] b) 8.0 m/s2 ? [4 N] 3. What acceleration would an unbalanced force of 84 N produce on each of the following masses? a) 4.2 kg [20 m/s2] b) 8.4 kg [10 m/s2] 4. A 1200 kg car traveling at 50 km/h experiences an air resistance of 5000 N and road friction of 2200 N. If the wheels push with a force of 7500 N, what is the car’s acceleration? [0.250 m/s2] 5. Two boys, one with a mass of 60 kg an the other with a mass of 90 kg, are standing side by side in the middle of an ice rink. One of them pushes the other with a force of 360 N for 0.10 s. Assuming that the ice surface is frictionless: a) What is the acceleration of each boy? [6.0 m/s2, 4.0 m/s] b) What speed will each boy reach after the 0.10 s? [0.60 m/s, 0.40 m/s] c) Does it matter which boy did the pushing? 6. A car is traveling along an expressway at 90 km/h. The driver spots a stalled car and some traffic congestion on the road ahead, and so applies the brakes. The braking action causes a frictional force of 8400 N to act on the 1050 kg car. a) What is the acceleration of the car when the brakes are applied?[-8.0 m/s2] b) How long does it take for the car to stop? [3.0 s] c) How far does the car travel while it is braking? [39 m] 7. What change in velocity would be produced by an unbalanced force of 2.0 x 104 N acting for 6.0 s on a 2.0 x 103 kg dragster? [60 m/s] 8. Calculate the unbalanced force acting on a 4000 kg truck that changes its velocity from 22.0 m/s [N] to 8.0 m/s [N] in 3.50 s? [1.6 x 104 N [s] ] 9. Find the net force and acceleration of the following system. (Fnet=14.4 N[W34°S]; a = 0.58 m/s2 [W34°S]) 16 N

6N

8N 25 N

25 kg 5N

30 N

10. The engine of a 1650 kg truck applies a force of 17500 N [E]. If the truck starts from rest and the coefficient of friction between the tires and the road is 0.67, determine how far the truck travelled in 6.5 s. (85.1 m) 11. A 15 kg aluminum frame is slid along an aluminum path. What is the applied force if the object is accelerating at a rate of 2 m/s2? The coefficient of friction between the surfaces is 0.9. (162 N) 12. A 20 kg block site on a level surface, and a horizontal force of 65 N is applied to the block. a) If the coefficient of static friction between the block and the surface is 0.4, does the block move? (No) b) If not, how much force would be required to move the block? (>78 N) 13. A 50 kg box is being pulled by a force of 200 N at an acceleration of 2 m/s2. There is also a force of 10 N pushing against the box. Find the coefficient of kinetic friction. (0.18) 14. If the coefficient of friction is 0.25, how much horizontal force is needed to pull a 25 kg mass along a rough desk at a constant speed? [61 N] 15. What is the unbalanced force accelerating a 5.0 kg cannonball from rest to 150m/s [W], if the force acts for 0.050 s? 16. A 10 kg object is being pulled by 20 N at an angle of 15o to the horizontal. What is the acceleration of the object if the coefficient of kinetic friction is 0.15? [0.54 m/s2] 17. A 20.0 kg toboggan is pulled along at a constant speed by a force of 30 N at an angle of 25o. a) What is the force of gravity on the toboggan? [196 N] b) What is the coefficient of friction? [0.15] c) How much force (maintaining same angle) is needed to pull the toboggan if two 60.0 kg girls are sitting on it? [212 N] 18. A 100 kg packing crate is being pulled on a rough floor by a 200 N force, acting at 10o to the horizontal. How long does it take the crate to move 25 m if it’s initial velocity is 2 m/s? (µk = 0.2) [10.4 s]...