Download Mechanics #3

Dr. Campbell
15 HW Mechanics #3.docx
6 October 2015
AP Physics
Mechanics Homework #3
Dynamics #1
Name
Period
1. What average force is required to stop a 1000. kg car in 6.00 s if it is traveling at 45.0 m/s?
2. What is the weight, in Newtons, of a 70.0 kg astronaut;
a. on earth?
b. on the moon? (g = 1.70 m/s2)
c. on Jupiter? (g = 26.0 m/s2)
d. in outer space traveling with constant velocity?
3. Two boxes are sitting on a table. One has a mass of 5.0 kg and the other has a mass of 10.0
kg. A string connects them. Another string connects the 10.0 kg box and is pulled on
horizontally by student with a force of 100 N at an angle of 15° above the horizontal. Place Fg,
FN, T, and Fa in the drawing below. Calculate the normal force of each box and the tension in
the string. What is the horizontal acceleration of the boxes?
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Dr. Campbell
15 HW Mechanics #3.docx
6 October 2015
4. Below are top views of a block sitting on a frictionless surface. A 10.0 kg mass has the
following forces exerted upon it. Determine the magnitude and direction of the net force and the
acceleration of the box. Use an x-y table to solve. Do not solve using Law of Cosines.
a.
20.0 N
20°
40.0 N
40°
b.
30.0N
50.0 N
35°
110°
40.0 N
5. Three blocks are pulled along a frictionless surface by a horizontal 18.0 N force, as shown
below. Place Fg (both), FN (both), T1, T2, and Fa in the drawing below. Calculate the tension in
each string. What is the horizontal acceleration of the boxes?
18.0 N
1.00 kg
2.00 kg
2
3.00 kg
Dr. Campbell
15 HW Mechanics #3.docx
6 October 2015
6. Two blocks are attached as in the pulley system below. Place the forces in the drawing
below. Calculate the tension in the string. What is the acceleration of the boxes?
7.00 kg
5.00 kg
7. Two blocks are attached as in the pulley system below. Place Fg (both), and T in the drawing
below. Calculate the tension in the string. What is the acceleration of the boxes?
7.50 kg 3.50 kg
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Dr. Campbell
15 HW Mechanics #3.docx
6 October 2015
8. The block shown has a mass of 8.00 kg and lies on a smooth frictionless plane tilted at an
angle of θ = 20˚ to the horizontal. An applied force of 30.0 N is placed downward on the block
at an angle of 25º from the normal. Place Fg and FN in the drawing below. What is the
acceleration of the block? What is the normal force?
25º
30.0 N
20º
9. Three blocks are connected as shown below. (a) Draw all the forces that are present. (b)
Find the acceleration of the system. (c) Find the tension in each string.
T2
T1
5.00 kg
7.50 kg
4.00 kg
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Dr. Campbell
15 HW Mechanics #3.docx
6 October 2015
10. A window washer pulls herself upward using the bucket pulley apparatus shown below. (a)
How hard must she pull downward to raise herself slowly at constant speed? (b) If she increases
this force by 15%, what will her acceleration be? The mass of the person plus the bucket is 65.0
kg.
11. Two boats pull a 75.0 kg skier as shown below. (a) If each boat pulls with a force of 600. N
and the skier travels with a constant velocity, what is the magnitude of the retarding force
between the water and the skis? (b) Assuming the retarding force remains constant, if the boats
each pull with a force of 700. N, what is the magnitude of the acceleration of the skier?
45°
45°
5
Dr. Campbell
15 HW Mechanics #3.docx
6 October 2015
12. A 150. N bird feeder is supported by three cables as shown below. Find the tension in each
cable.
60°
30°
13. Consider a system where a block is connected to two springs as shown below. Both springs
have a constant of 25.0 N/m and the block is motionless. If the bottom spring is compressed
0.400 m past its equilibrium and the block has a mass of 3.00 kg, how far is the top spring
stretched past its equilibrium?
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