AP Physics 1 - 1.1 Scalars and Vectors in One Dimension- Exam Style questions- MCQs
Scalars and Vectors in One Dimension AP Physics 1 MCQ
Unit: 1. Kinematics
Weightage : 10-15%
Unit: 1. Kinematics
Weightage : 10-15%
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?
Correct answer: \( \boxed{\mathrm{B}} \)
The dots are recorded at equal time intervals, so the distance between consecutive dots represents the speed of the cart. Larger spacing means greater speed, and smaller spacing means lower speed.
At the beginning, the dots get farther apart. Since the cart is moving to the right and speeding up, the acceleration vector points to the right.
In the middle, the dots are approximately equally spaced. This means the speed is nearly constant, so the acceleration is \(a=0\).
At the end, the dots get closer together. The cart is still moving to the right, but its speed is decreasing. Therefore, the acceleration points opposite the direction of motion, which is to the left.
So the acceleration pattern is: beginning to the right, middle \(a=0\), and end to the left. This matches choice \( \boxed{\mathrm{B}} \).
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.
Correct answer: \( \boxed{\mathrm{D}} \)
The dots are recorded at equal time intervals, so the spacing between consecutive dots represents the speed of the object. Smaller spacing means smaller speed, and larger spacing means larger speed.
On the way up, the dots get closer together as the object rises. This means the object is slowing down, so the upward velocity vectors should get shorter.
At the highest point, the vertical velocity is momentarily \(0\), but the acceleration is still downward due to gravity.
On the way down, the dots get farther apart as the object falls. This means the object is speeding up downward, so the downward velocity vectors should get longer.
Therefore, the students have correctly shown the vectors getting shorter on the way up and longer on the way down. This matches choice \( \boxed{\mathrm{D}} \).