AP Physics C Mechanics Scalars and Vectors MCQ

Scalars and Vectors in One Dimension AP  Physics C Mechanics MCQ – Exam Style Questions etc.

Scalars and Vectors in One Dimension AP  Physics C Mechanics MCQ

Unit: 1. Kinematics 

Weightage : 10-15%

AP Physics C Mechanics Exam Style Questions – All Topics

Question

                                                                           

Figure 1 shows a person dropping a coffee filter to the floor. As the filter drops, air resistance will cause the acceleration to decrease with time. Figure 2 shows the velocity v and acceleration a  vectors a short time after the filter is dropped. Which of the following could show the velocity and acceleration vectors a short time after Figure 2?

 
 
Answer/Explanation

Ans:D

Since the acceleration and velocity are both downward, the velocity should increase over time. Therefore, since the velocity is increasing and the acceleration is decreasing over time, the velocity vector should be larger and the acceleration vector should be smaller.

Question

The acceleration vector for the first three seconds of an object moving with constant acceleration is shown.   

Answer/Explanation

Ans:E

The acceleration is constant and to the right. So, the velocity vector must increase toward the right. This solution shows the velocity starting at zero and increasing toward the right.

Question                                                                    

                                                                                                                                      

Starting from rest, a cart moves to the right in a straight line along a track. The motion of the cart is represented by the dots shown, recorded at equal time intervals. Which of the following best represents the acceleration vectors at the beginning, middle, and end of the motion?

 
 
 
Answer/Explanation

Ans:B

The distances between the dots represent the speed of the cart. The dots first get farther apart, indicating an increasing speed to the right. This indicates an acceleration to the right. Next, the dots are approximately equally spaced in the middle. This indicates an acceleration of zero. Then the dots get closer together, indicating a decreasing speed to the right. This indicates an acceleration to the left.

Question

                 

In an experiment, an object is launched with an initial velocity in the vertical direction. Its position as a function of time is recorded as dots on a piece of paper, as shown, with the downward motion offset to the right of the upward motion. Students draw the velocity vectors shown to represent the speed and direction of the object as it moves. Which of the following correctly describes the relationship between the dots and the vectors?

A The dots are getting higher over time, so the students’ vectors should get longer at higher positions, not smaller.

B The dots are getting higher over time, so the students have correctly shown the vectors getting smaller at higher positions.

C The dots are getting closer together on the way up and farther apart on the way down, so the students should show the vectors getting longer on the way up and shorter on the way down, the reverse of what is shown.

D The dots are getting closer together on the way up and farther apart on the way down, so the students have shown the vectors getting shorter on the way up and longer on the way down.

E Since the dots show the object moving in free fall, the students should draw all the vectors as the same size.

Answer/Explanation

Ans:D

On the way up, as the object gets higher, the dots get closer together. This indicates that the speed for each time interval is decreasing, so the vectors should be getting smaller. On the way down, as the object gets lower, the dots get further apart. This indicates that the speed for each time interval is increasing, so the vectors should be getting larger.

Question

Which of the following quantities, if any, is a scalar quantity?
(A) A velocity of −2.0 m/s
(B) A potential energy of −2.0 J
(C) A momentum of −2.0 N∙s
(D) A displacement of −2.0 m
(E) None of the above is a scalar quantity.

Answer/Explanation

Ans:C

Displacement, velocity, and momentum are vector quantities because their direction matters. When using a negative sign with these, the negative indicates a direction. However, all forms of energy are scalar quantities, just amounts with no direction. The negative sign on potential energy simply means an amount of potential energy less than zero.

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