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1. a) If an automobile of mass 1600 kg accelerates at 4.5 m/s2, what would be the net force on
the vehicle?
b) A horizontal force of 64 N is applied to a wagon of mass 20 kg. What is the acceleration
of the wagon
c) A net force of 240 N causes a block of iron to accelerate across a
smooth level surface at 2.5 m/s2. What is the mass of the iron block?
2. An electron is accelerated over a distance of 4.0 mm by an electrical force of 5.6 X 10-15 N.
Since the electron has a mass of 9.11 X 10-31 kg, what is its acceleration and final velocity?
3. A 3.0 kg toy starts from rest and is pulled by a force of 24 N. How far will it travel in 5.0 s?
4. An 8.0 g bullet takes 4.0 X 10-4 s, to pass through a heavy block of wood. Before striking the
wood, it travels at 400 m/s. Upon emerging it has a velocity of 100 m/s. Ignore any motion of
the wood.
a) What force did the wood apply to the bullet?
b) Determine the thickness of the block of wood?
5. A motorist is driving at 72 km/h when she sees a child run onto the road 40 m ahead. Her
reaction time is 0.60s, and the mass of the car is 1000 kg. If the average braking force is
8000 N, will she be able to stop in time?
6. A net force of 8.0 N gives a mass Ml an acceleration of 2.0 m/s2. With the same force, M2 has
an acceleration double that of M1. If the two masses were attached, what acceleration would
the force give them?
7. Two forces as shown in the diagram act on a 5.0 kg mass.
a) What is the net force on the object?
b) Determine the object's acceleration.
8. A smooth plane, inclined to the horizontal at an angle of 15o has a block of mass 2.0 kg on it.
a) Calculate the acceleration of the block down the plane?
b) If it takes 1.5 s to reach the bottom after being released from rest, how far up the
plane was the block released?
9. A 20 kg lawn mower has a handle which makes an angle of 60o to the ground. If a 150 N
force is applied to the handle, and the friction is 25 N, what is the acceleration of the mower?
10. Two girls pull a sled across snow. Each applies a force of 10 N. One applies the force at
an angle of 30o to straight forward, while the other applies the force at an angle of -40o to
straight forward. A third girl pulls straight backwards with a 2.0 N force. If the mass of the
sled is 10 kg, determine its instantaneous acceleration.
11. What is the reaction force for each of these action forces?
a) the southward force of a soccer players foot on the ball.
b) the backward force of your foot on the ground when you walk.
c) the downward force of a tire on the road.
d) the backward force of a rocket motor on its exhaust gases.
e) the downward pull of a climbers hands on the rock making up the cliff.
12. A person is in the center of a lake with friction less ice on it. Besides waiting until spring and
swimming to shore, how can the person get off the lake?
13. With what force does a boy of mass 30 kg have to pull on a rope attached to a cart with a
mass of 100 kg on it, in order to accelerate the cart at 2.0 m/s2? What reaction force must the
ground apply to his feet in order to prevent him from moving towards the cart? In the absence
of friction, what is the boy's acceleration?
14. Two gliders, the first in line of mass 1600 kg, and the second in line of mass 800 kg, are
attached by towropes to each other, and to an airplane which will pull the gliders down a
runway for take off. The air resistance (frictional drag), can be assumed to be constant at
2000 N on each glider. The towrope between the gliders and the tow plane can withstand a
maximum tension of 10 000 N.
a) How long a runway is needed, if a velocity of 40 m/s is required for takeoff,?
b) What tension must the towrope between the gliders be able to withstand?
15. Different numbers of elastic bands are used to accelerate a cart. The graph shows acceleration
versus force exerted by the elastic bands.
a) Determine the mass of the cart.
b) Explain why the graph does not go through zero.
November 19, 2013
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