Homework solution
Chapter 3
Dr. Ray Kwok
SJSU
Kinematics - Dr. Ray Kwok
Chapter 3
3. Is it a fine for speeding based on one’s average speed or one’s
instantaneous speed? Explain.
Instantaneous speed is what the radar gun reads.
6. Can an automobile with a velocity toward the north simultaneously
have an acceleration toward the south? Explain.
Yes, the car can move toward the north but decelerate.
10.You are driving north on a highway. Then, without changing speed,
you round a curve and drive east.
a. Does your velocity change?
Yes, velocity change because the direction changes.
b. Do you accelerate? Explain.
Yes, change of velocity means there has to be acceleration.
Kinematics - Dr. Ray Kwok
20. Suppose that the 3 balls in exercise 19 start simultaneously from the
tops of the hills. Which one reaches the bottom first? Explain.
The middle one because the ball goes down with faster acceleration
first, so higher average speed.
26. Suppose that the freely falling object in the preceding exercise were
also equipped with an odometer. Would the readings of distance fallen
each second indicate equal or different falling distances for successive
seconds?
During each successive second, the object falls faster and covers
greater distance.
Kinematics - Dr. Ray Kwok
30. Someone standing at the edge of a cliff (as in Figure 3.9) throws a ball
nearly straight up at a certain speed and another ball nearly straight
down with the same initial speed. If air resistance is negligible, which
ball will have the greater speed when it strikes the ground below?
Same speed.
40. Two balls are released simultaneously from rest at the left end of
equal-length tracks A and B as shown. Which ball reaches the end of
its track first?
B. The ball picks up higher average speed as it goes down the lower
part.
Kinematics - Dr. Ray Kwok
30. Someone standing at the edge of a cliff (as in Figure 3.9)
throws a ball nearly straight up at a certain speed and
another ball nearly straight down with the same initial
speed. If air resistance is negligible, which ball will have
the greater speed when it strikes the ground below?
Same speed.
43. Why does a stream of water get narrower as it falls from a
faucet?
As water falls it picks up speed. Since the amount of water
falls from faucet remains the same, it stretches out as
distance increases.