Download Unit B UA pt. A: Forces

6/22/2017
P20 Unit B –
Dynamics UA pt. A
Name: _______________
Date: _______________
1. If you get to your feet in a canoe and move towards the front, the canoe
moves in the opposite direction. Explain why. (2 marks)
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2. A net force of 2.5 x 103 N acts on an object for 5.0 s. During this time, the object
accelerates from rest to a velocity of 48 km/h. What is the mass of the object? (9.4 x 102
kg) (2 marks)
3. Atwood’s Pulley: A 3.0 kg mass is attached to a 5.0 kg mass by a string that passes
over a frictionless pulley. Find the following values when the masses are allowed to hang
freely:
a) acceleration of the system (2.5 m/s2) (2 marks)
b) magnitude of the tension in the string (37 N) (2 marks)
4. A 9.6 kg sled is pulled along firmly packed snow (which is level). If the coefficient of
kinetic friction between the surfaces is 0.11, what is the magnitude of the force of friction
acting on the sled? (10 N) (1 mark)
5. A 20.0 N box is placed on the floor. A force of 3.0 N is required to keep the object
moving at a constant speed. Find the coefficient of kinetic friction between the two
surfaces. (0.15) (2 marks)
6. An 8.0 g bullet traveling at 400 m/s passes through a heavy block of wood in
4.0 x 10-4 s, emerging with a velocity of 100 m/s. Ignore any motion of the wood.
a) With what average force did the wood oppose the motion of the bullet? (-6.0 x 103 N)
(2 marks)
b) How thick is the wood? (1.0 x 10-1 m) (2 marks)
7. Why is the coefficient of kinetic friction always smaller than the coefficient of static
friction? (2 marks)
8. Fletcher’s Trolley: A 5.0 kg mass rests on a level frictionless table and is attached to a
3.0 kg mass by a string that passes over a frictionless pulley. Find the tension in the
string when the masses are released. (18 N) (3 marks)
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6/22/2017
9. Fletcher’s Trolley: A steel block rests on a level table and is attached to a 5.0 kg mass
by a string that passes over a frictionless pulley. There is 24 N of friction present
between the steel block and the table. If the acceleration of the system is 2.9 m/s2, find
the mass of the steel block. (3.6 kg) (3 marks)
Use the following diagram to answer the next question.
10. The diagram shows a 1.20 kg cart on top of a table attached to two masses by strings
going over frictionless pulleys. The coefficient of kinetic friction between the cart and the
table is 0.140. If the mass of m is 1.00 kg and the mass of M is 2.00 kg, what is the
acceleration of the cart? (1.94 m/s2) (3 marks)
Use the following diagram to answer the next question.
11. A sign is suspended by three ropes, R, S and T. Each rope as a force of tension
associated with it. Order the ropes from the least amount of tension to the most amount of
tension (give qualitative or quantitative explanations for your answer, or you will not
receive any marks!) (R<T<S) (2 marks)
12. A 10 kg block on a 30º slope. If the coefficient of friction is 0.30 determine the
following:
a) the force of friction. (25 N) (1 mark)
b) the force of gravity parallel to the slope. (49 N) (1 mark)
c) the acceleration of the block down the slope. (2.4 m/s2) (1 mark)
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Dept. of “Forcing” you to do this unit assignment!
6/22/2017
d) The minimum coefficient of friction needed to prevent the block from sliding. (0.58)
(1 mark)
13. If a stationary rock climber with a mass of 70.0 kg is suspended so that
the rope makes an angle 10.0º from the vertical. Determine the tension in
the rope. (676 N) (2 marks)
14. Two gold bricks are connected by a light rope and pulled across a table with a force of 75 N.
The force of friction acting on the blocks is 25 N. Calculate the acceleration of
the blocks.
(2 marks)
(1.0 m/s2)
Bonus Questions: Answer only ONE!!!
Fair Bonus Question: Terminal velocity is the speed at which the air resistance acting on a falling object is equal to the acceleration
due to gravity and the falling object stops accelerating and falls with uniform motion. The terminal velocity of a human with
outstretched arms is around 190 km/h. If a human is dropped from 3.00 km in the air, calculate the time it takes the human to hit the
ground, taking air resistance into account.
Unfair Bonus Question: Make an analysis of the forces acting on Wile E. Coyote when he pursues the Road Runner off of a cliff.
LD Industries
Dept. of “Forcing” you to do this unit assignment!