Download Review Game

Unit 3 – Review Game Questions
1. Glaciers push rocks in front of them. Before a stationary rock starts moving as a result of the force
Fglacier exerted on it, the static friction between the rock and the ground
a. decreases until it is smaller than Fglacier.
b. remains constant until it is smaller than Fglacier.
c. increases until it is equal to the product of s and the normal force on the rock.
d. decreases until it is equal to the product of s and the normal force on the rock.
2. Two balls are thrown horizontally. Ball C is thrown with a force of 20 N, and ball D is thrown with a
force of 40 N. Assuming all other factors are equal, ball D will fall toward the ground
a. faster than ball C.
b. more slowly than ball C.
c. at the same rate as ball C.
d. at a rate that can’t be compared with ball C using the information given.
3. For the winter, a duck flies 10.0 m/s due south against a gust of wind with a speed of 2.5 m/s. What is
the resultant velocity of the duck?
Figure 1
4. Refer to Figure 1. How many displacement vectors shown in the figure above have horizontal components?
5. Refer to Figure 1. How many displacement vectors shown in the figure above have components that
lie along the y-axis and are pointed in the –y direction?
6. What is the path of a projectile (in the absence of friction)?
Figure 2
The figure shows the path of a ball tossed from a building. Air resistance is ignored.
7. Refer to Figure 2. At what point of the ball’s path is the vertical component of the ball’s velocity zero?
8. Refer to Figure 2. At which location is the magnitude of the ball’s velocity the least?
9. Refer to Figure 2. At which location is the magnitude of the ball’s velocity greatest?
10. Refer to Figure 2. The horizontal component of the ball’s velocity at A is __________.
11. Refer to Figure 2. At which point in the figure is the ball’s speed about equal to the speed at which it
was tossed?
12. Refer to Figure 2. What would happen to the width of the ball’s path if it were launched with a
greater velocity?
13. Refer to Figure 2. In the figure, what would happen to the height of the ball’s path if it were
launched with a greater velocity?
14. Refer to Figure 2. Describe the graph of the horizontal component of velocity versus time for the
motion of the ball shown in the figure.
15. Refer to Figure 2. Describe the graph of the vertical component of velocity versus time for the motion of the ball shown in the figure. Identify any constants that would appear in the graph.
Figure 3
16. In Figure 3, which diagram represents the vector addition C = A + B?
17. The length of a vector arrow in a diagram is proportional to what property of the vector?
18. What is a resultant?
19. Briefly explain the triangle (or polygon) method of addition.
20. The equation
is valid only if Δx and Δy are magnitudes of vectors that have what
orientation with respect to each other?
21. What is a projection of a vector along an axis of a coordinate system called?
22. Breaking a vector into two components is given what term?
23. How can you use the Pythagorean Theorem to add two vectors that are not perpendicular?
24. A ball rolls off the edge of a table. Describe what happens to the horizontal component of velocity.
25. As the angle of an inclined plane increases, what happens to the parallel component of the weight?
26. A quantity that has both magnitude and direction is a(n)_______.
27. An athlete runs 125 m across a level field at an angle of 30.0 north of east. What is the north component of this displacement?
28. A projectile is launched at an angle into the air. Neglecting air resistance, what is its vertical acceleration?
29. In the absence of air resistance, why does the horizontal component of velocity for a projectile remain constant while the vertical component changes?
30. What is the range of possible values for the resultant of two vectors with magnitudes of 4 and 5
units?
31. Construct an FBD for this situation: A 25.0 N force is applied to a crate at an angle of 30 in order to
accelerate it rightward across a rough, horizontal surface.
32. Construct an FBD for the following situation: A large crate is slowly accelerated down a steep and
rough inclined plane.
33. Which of the following are always true of an object in equilibrium?
a. All the forces acting upon the object are equal.
b. The object is at rest.
c. The object is moving and moving with a constant velocity.
d. The object has an acceleration of zero.
e. There is no change in the object’s velocity.
f. The sum of all the forces is 0 N.
g. All the forces acting upon an object are balanced.
34. An object rests upon an inclined plane. If the angle of incline is increased, then the normal force
would _______.
a. increase
b. decrease
c. remain the same
35. Briefly explain why the true path of a projectile traveling through Earth’s atmosphere is not a
parabola.
36. In a free-body diagram of an object, why are forces exerted by the object not included in the diagram?
37. The length of the force vector is proportional to what property of a force?
38. In the equation form of Newton’s second law, ∑F = ma, what does ∑F represent?
39. In the equation Fnet = ma, what is the direction of the acceleration?
Unit 3– Review Game Answers
1. Choice c is correct. As a force is exerted on a stationary object, static friction increases with the force
applied until the force applied equals the product of the coefficient of static friction and the normal force
exerted upward on the rock. When the applied force exceeds the product of the coefficient of static friction and the normal force, the rock starts to move.
2. C is correct. The horizontal force exerted on a projectile does not affect the downward (gravitational)
acceleration of the projectile. Since both balls are thrown horizontally, they both have vyi = 0. Therefore,
the balls will fall at the same rate, both accelerating at 9.80 m/s2 toward the ground.
3. 7.5 m/s south
Given
v = 10.0 m/s south
v = 2.5 m/s north
Solution
vR
4. 4 – d1, d3, d4 and d5
5. 2 – d4 and d5
6. a parabola
7. B
8. B.
9. D.
10. equal to the horizontal component of its initial velocity.
11. C
12. The width of the ball’s path would increase.
13. The height of the ball’s path would increase.
14. The graph of the horizontal component of the velocity versus time is a straight line parallel to the
time axis.
15. The graph of the vertical component of the velocity versus time is a straight line with a negative
slope. The slope of the line is -9.81 m/s .
16. II
17. The length of the vector arrow is proportional to the magnitude of the vector.
18. A resultant is a vector that represents the sum of two or more vectors.
19. The triangle method of adding vectors requires that you align the vectors, tail to tip, by moving them
parallel to their original orientations. The resultant vector is an arrow drawn from the tail of the first
vector to the tip of the last vector.
20. The vectors must be perpendicular to each other.
21. a component of the vector
22. resolving the vector
23. Resolve each vector into perpendicular components and add the components that lie along the same
axis. The resultant vectors can be added by using the Pythagorean theorem because they are perpendicular.
24. The horizontal velocity remains constant.
25. the parallel component decreases
26. vector
27. 62.5 m
28. the vertical acceleration is the acceleration due to gravity (g)
29. There is no horizontal component of gravitational force.
30. When the vectors are aligned in the same direction, their maximum value is 9 units. When the vectors oppose each other their minimum value is 1 unit. When the vectors are aligned at some angle to
each other, their resultant would have a value between 9 units and 1 unit.
31. Note: The x component of the applied force needs to be larger than the friction force.
32. Note: The x component of the weight down the inline is greater than the friction force.
33. d, e, f, and g
34. decrease
35. With air resistance, a projectile slows down as it collides with air particles. Therefore, the true path
of a projectile would not be a parabola.
36. Forces exerted by the object do not change its motion.
37. magnitude
38. ∑F is the vector sum of the external forces acting on the object.
39. The acceleration is in the direction of Fnet.