Physics 11 Final Exam: Review - Kinematics
1. Two cars collide head on without the driver of either one having hit the brakes.
a. Is it possible that both cars had the same velocity just prior to the collision?
b. Is it possible that both cars had the same speed just prior to the collision?
Explain your answers.
2. Car A collides into the rear end of car B without the driver of car A hitting his brakes.
a. Is it possible that both cars had the same velocity just prior to the collision?
b. Is it possible that both cars had the same speed just prior to the collision?
Explain your answers.
3. An car moving due east, travels at 6.7 m/s for 7.3 seconds, then at 4.2 m/s for 6.4 seconds.
a. What total distance has it traveled?.
b. For what total time interval was the car moving?
c. What was the average speed of this car during the entire time interval?
Can we calculate the average speed by dividing the sum of the two individual speeds by two?
4. The graph to the right represents the position as a function of time for an object that is moving back and forth along a straight line. For each of the intervals:
a. indicate whether the velocity is positive negative, or zero.
b. indicate whether the speed is increasing or decreasing.
indicate whether the acceleration is positive, negative, or zero.
5. Students frequently have trouble distinguishing between velocity and acceleration when the velocity of an object is itself zero. The following series of questions are meant to help you confront and overcome these difficulties. Pretend that you are studying the motion of sprinter along a track. You are using a stopwatch to measure the time and a radar gun to measure the sprinter’s speed . If the sprinter has a constant acceleration, a chart of her speed at various times might look like this:
TIME (s) VELOCITY (m/s)
0.0 0.0
0.1 1.5
0.2 3.0
0.3 4.5
0.4 6.0
0.5 7.5
a. Explain how the chart shows that the sprinter’s acceleration remains constant.
b. What is the average acceleration between 0.0 seconds and 0.5 seconds?
c. What is the average acceleration between 0.0 seconds and 0.2 seconds?
d. What is the average acceleration between 0.0 seconds and 0.1 second?
e. 0.05 seconds is not listed on the chart, but what do you think the average acceleration between 0.0 seconds and 0.05 seconds must be?
f. What do you think the average acceleration between 0.0 seconds and 0.000001 seconds must be?
g. The sprinter’s speed at 0.0 seconds was zero. Should we also say that her instantaneous acceleration at zero seconds was zero, or should we say that it was another value? Explain your answer.
h. If the sprinter’s acceleration at 0.0 seconds was zero, would she have been able to start moving? Explain your answer
i. In general, if an object’s velocity is zero must its acceleration also be zero? Explain your answer.
j. Since the sprinter’s acceleration is constant, a graph of her velocity versus time would look like the graph pictured below. Based on this graph, draw a graph of the sprinter’s acceleration versus time.
k. Now look at the graph you just drew. What is the acceleration of the sprinter at zero seconds? Is her acceleration zero just because her speed is zero?
l. Do you want to reconsider the answer you gave to part “i” above. If an object’s speed is zero must its acceleration also be zero?
6. A car has an initial speed of 16.7 m/s and accelerates at 2.5 m/s2 for another 8.1 seconds. What is the final speed of the car?
7. A car is initially moving at 28.4 m/s. In a panic stop the car can decelerate (slow down) with an acceleration of - 3.8 m/s2. (The acceleration is negative because the car is slowing down.) What is the least amount of time it will take for this car to come to rest?
8. A car moving with a uniform (constant) acceleration takes 3.5 seconds to accelerate from 22 m/s to 34 m/s. Through what distance does the car move during this period of acceleration?
9. What acceleration must a car have if, starting from rest, it travels 30 meters in 3.5 seconds?
10. A rocket is blasting off with a constant upward acceleration of 18.7 m/s2. Through what vertical height will the rocket rise as its speed changes from 3.6 m/s to 8.5 m/s?
11. A ball is thrown vertically upward with an initial speed of 36.4 m/s.
a. How high will it be after 2.7 seconds?
b. What will its speed be after 2.7 seconds?