1. Starting from rest and moving in a straight line, a runner achieves a velocit
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Question
1. Starting from rest and moving in a straight line, a runner achieves a velocity of 6 m/s in a time of 4 s. What is the average acceleration of the runner?
_____ m/s2
2. Starting from rest, a car accelerates at a rate of 2.7 m/s2 for a time of 3 seconds. What is its velocity at the end of this time?
m/s
3. Does the speedometer on a car measure average speed or instantaneous speed?
average speed
instantaneous speed
Explain.
4. A ball attached to a string is whirled in a horizontal circle such that it moves with constant speed.
(a) Does the velocity of the ball change in the process? Explain.
A. Yes, neither the velocity nor the speed are constant.
B. No, there is constant velocity and constant speed.
C. There is not enough information to determine whether the velocity is constant.
D. Yes, the velocity is not constant although the speed is constant.
(b) Is the acceleration of the ball equal to zero? Explain.
A. Yes, the acceleration of the ball is equal to zero because of the non-zero velocity of the ball.
B. No, the acceleration is not zero, as a non-zero acceleration is needed to change velocity.
C. There is not enough information to determine the acceleration of the ball.
5. A driver of a car steps on the brakes, causing the velocity of the car to decrease. According to the definition of acceleration provided in this chapter, does the car accelerate in this process? Explain.
A. Yes, acceleration is the change in velocity per unit time, whether that change is positive or negative.
B. No, the car is not increasing in velocity over an interval of time.
C. There is not enough information to determine whether or not the car is accelerating.
A. Yes, neither the velocity nor the speed are constant.
B. No, there is constant velocity and constant speed.
C. There is not enough information to determine whether the velocity is constant.
D. Yes, the velocity is not constant although the speed is constant.
Starting from rest and moving in a straight line, a runner achieves a velocity of 6 m/s in a time of 4 s. What is the average acceleration of the runner? m/s2 Starting from rest, a car accelerates at a rate of 2.7 m/s2 for a time of 3 seconds. What is its velocity at the end of this time? m/s Does the speedometer on a car measure average speed or instantaneous speed? average speed instantaneous speed A ball attached to a string is whirled in a horizontal circle such that it moves with constant speed. Does the velocity of the ball change in the process? Explain. Is the acceleration of the ball equal to zero? Explain. A driver of a car steps on the brakes, causing the velocity of the car to decrease. According to the definition of acceleration provided in this chapter, does the car accelerate in this process? Explain.Explanation / Answer
1)
This can be solved using the formula vf = vi +at where vi is the initial velocity(0 m/s since the runner was at rest);
You end up with the formula a = (vf-vi)/t = (6-0)/4 = 1.5 m/s^2
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2)
V=AT
=2.7*3
=8.1 M/S
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3)It shows instantaneous speed - the speed of the car at the very moment. Note that the answer "average speed" is obviously wrong because you need to define an interval of time over which to measure distance if you want to measure average speed, and then similarly "velocity" is wrong because the speedometer doesn't tell you the car's direction.
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4) Yes, the velocity is not constant.
b'coz direction is changing continuously
(b) No, the velocity is not constant so acceleration is also not constant
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5)No, the car is not increasing in velocity over an interval of time.
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