Physics Chapter 3

part c) What is the change in its velocity during this 1-ss interval?

-10 m/s

part d) What is its velocity 1 ss after it reaches its highest point?

-10 m/s

part e) What is the change in velocity during this 1-ss interval?

-10 m/s

part h) What is the acceleration of the ball at the moment the ball has zero velocity?

-10 m/s2

part f) What is the change in velocity during the 2-ss interval? (Careful!)

-20 m/s

A ball is tossed with enough speed straight up so that it is in the air several seconds. Assume upward direction is positive and downward is negative. Part a) What is the velocity of the ball when it reaches its highest point?

0 m/s

Surprisingly, very few athletes can jump more than 2 feet (0.6m) straight up. Use d=1/2gt and solve for the time one spends moving upward in a 0.6-m vertical jump. Then double it for the "hang time"-the time one's feet are off the ground.

0.70s

Part B) What is its velocity 1 s before it reaches its highest point?

10 m/s

What is the speed over the ground of an airplane flying at 100 km/h relative to the air caught in a 100-km/h right-angle crosswind?

141 km/h

What exactly is meant by a "freely falling" object?

An object in free fall falls under gravity alone with no friction.

What relationship between distance traveled and time did Galileo discover for freely falling objects released from rest?

Galileo discovered that distance increased as the time squared.

Why does the distance traveled by the ball in each half second after it is released change in the way in which it does?

Gravity is pulling down on the ball, so it accelerates down at a steady rate.

What is the distance fallen for a freely falling object 1 s after being dropped from a rest position? What is the distance for a 4-s drop?

It falls 5 m in 1 s and 80 m in 4 s.

If a car is moving at 90 km/h and it rounds a corner, also at 90 km/h, does it maintain a constant speed? A constant velocity?

It maintains a constant speed, but does not maintain a constant velocity.

A friend says that if a car is traveling toward the east, it cannot at the same time accelerate toward the west. What is your response?

The friend is wrong. When acceleration of the car is in direction opposite to its velocity, the car is decelerating.

Acceleration is generally defined as the time rate of change of velocity. When can it be defined as the time rate of change of speed?

When moving in a straight line, the time rate of change of speed is acceleration.

As you read this in your chair, how fast are you moving relative to the chair? Relative to the Sun?

You are not moving relative to the chair, but you are moving over 100,000 km/h relative to the Sun.

Select the correct equations that show that the acceleration of a hamster is 5 m/s2 when it increases its velocity from rest to 10 m/s in 2 s.

a=Δv/t=(10m/s)/(2s)=5m/s2

How can you use the graph of velocity versus time to estimate the acceleration of the ball?

by estimating the value of the slope of the graph

What two units of measurement are necessary for describing speed?

distance and time

How does the distance traveled by the ball in the second half second compare with the distance traveled by the ball in the first half second?

increases

What kind of speed is registered by an automobile speedometer?

instantaneous speed

Select the correct equations that show that a freely falling rock drops a distance of 80m when it falls from rest for 4 s

s=g⋅t2/2=(10m/s2)⋅(4s)2/2=80m

Select the correct equations that show that the average speed of a rabbit that runs a distance of 36 m in a time of 3 s is 12 m/s .

v=s/t=(36m)/(3s)=12m/s

A rowboat heads directly across a river at a speed of 3 m/s. Select the correct equations that show that if the river flows at 4 m/s, the speed of the boat relative to the riverbank is 5 m/s

v=v21+v22√=(3m/s)2+(4m/s)2√=5m/s