Physics Chapter 3
A mosquito flying at 3 m/s that encounters a breeze blowing at 3 m/s in the opposite direction has a speed of
0 m/s
An object covers a distance of 8 meters in the first second of travel, another 8 meters during the next second, and 8 meters again during the third second. Its acceleration is
0 m/s^2
A cart changes its speed from 90 m/s to 100 m/s in 10 seconds. During this interval its acceleration is
1 m/s^2
A river 100 m wide flows 1 m/s due south. A boat that travels 1 m/s relative to the water is pointed due east as it crosses from the west bank. Relative to its starting point, the boat travels
141 m
Phil leans over the edge of a cliff and throws a rock upward at 5 m/s. Neglecting air resistance, two seconds later the rock's speed is
15 m/s
The time it takes a car to attain a speed of 30 m/s when accelerating from rest at 2 m/s^2 is
15 s
Jogging Jake runs at 4 m/s along a train flatcar that moves at 10 m/s in the opposite direction. Jake's speed relative to the ground is
6 m/s
If a car increases its velocity from zero to 60 m/s in 10 seconds, its acceleration is
6 m/s^2
At one instant an object in free fall is moving downward at 50 m/s. One second later its speed is
60 m/s
Phil standing at the edge of a cliff throws one ball straight up and another ball straight down, both with the same speed. Neglecting air resistance, which ball hits the ground below with the greater speed?
Neither, both hit with he same speed
An airplane that flies at 100 km/h in a 100 km/h crosswind has a ground speed of
141 km/h
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-able crosswind?
141 km/h
A motorboat that normally travels at 8 km/h in still water heads directly across a 6 km/h flowing river. The resulting speed of the boat is about
10 km/h
What is the acceleration of a car moving along a straight toad that increases its speed from 0 to 100 km/h in 10 s?
10 km/h-s
If a freely falling object were equipped with a speedometer, its speed reading would increase each second by about
10 m/s
If you throw a ball straight downward (in the absence of air resistance), after leaving your hand its acceleration is
10 m/s^2
Neglecting air resistance, a bullet fired straight down from the top of a high cliff has an acceleration of
10 m/s^2
When a ball thrown straight upwards reaches the very top of its path, it acceleration is
10 m/s^2
An 80-km/h airplane caught in a 60 km/h crosswind has a resultant speed of
100 km/h
A river 100 m wide flows 1 m/s due south. A boat that travels 1 m/s relative to the water is pointed due east as it crosses from the west bank. The boat reaches the east bank
100 m farther south
If a stone falls to the bottom of a mine shaft in 6 seconds, then the depth of the shaft is about
180 m
A ball starting from rest at the top of an inclined plain gains a speed of 2 m/s for each second it rolls. What is its acceleration down the incline?
2 m/s^2
The total time it takes a projectile fired straight up at 10 m/s to reach the top of its path and return to its starting point is about
2 s
The average speed of a horse that gallops 10 km in 30 min is
20 km/h
When you walk at an average speed of 4 m/s, in 5 s you'll cover a distance of
20 m
An object at rest near the surface of a distant planet starts to fall freely. If the acceleration there is twice that of the Earth, its speed one second later would be
20 m/s
If a freely falling object were equipped with a speedometer on a planet where the acceleration due to gravity is 20 m/s^2, then its speed would increase each second by
20 m/s
An object falls freely from rest on a planet where the acceleration due to gravity is twice as much as on Earth. In the first 5 seconds it falls a distance of
250 m
What is the average speed in km/h of a horse that gallops a distance of 15 km in a time of 30 min?
30 km/h
A pot that falls from a ledge and hits the ground 45 m below hits the ground at
30 m/s
If a rocket initially at rest accelerates at a rate of 50 m/s^2 for one minute, its speed will be
3000 m/s
Ten seconds after starting from rest, a car is moving at 40 m/s. What is the car's acceleration?
4 m/s^2
What is the acceleration of a car that starts from rest and 5 seconds later reaching a speed of 20 m/s?
4 m/s^2
At one instant a heavy object in air is moving upward at 50 m/s. One second later its speed is about
40 m/s
In its first second of free fall, a dropped softball will fall with a vertical distance of
5 m
One half second after stating from rest, a freely falling object will have a speed of about
5 m/s
Phil leans over the edge of a cliff and throws a rock upward at 5 m/s. Neglecting air resistance, one second later the rock's speed is
5 m/s
A car's speed 3 seconds after accelerating from rest at 2 m/s^2 is
6 m/s
A mosquito flying at 3 m/s that encounters a breeze blowing at 3 m/s in the same direction has a speed of
6 m/s
A ball starting from rest a the top of an inclined plane accelerates at 2 m/s^2 and reaches the bottom of the plane in 3 seconds. What is the length of the plane?
9 m
A free-falling watermelon falls with constant
Acceleration
Galileo discovered that when air resistance can be neglected, all objects fall with the same
Acceleration
When we are talking about how quickly "how fast" changes, we're talking about
Acceleration
What is the effect of air resistance on the acceleration of falling objects?
Air resistance decreases the acceleration of falling objects
What exactly is meant by a "freely falling" object?
An object in free fall falls under gravity alone with no friction
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
If an object moves with constant acceleration, its velocity must
Change by the same amount each second
Which best describes what occurs when a body accelerates?
Change in velocity per unit time
A vehicle undergoes acceleration when it
Changes its direction, loses speed, and gains speed
A ball tossed vertically upward rises, reaches its highest point, and then falls back to its starting point. During this time the acceleration of the ball is always
Directed downward
The difference between speed and velocity involves
Direction
Why does the distance traveled by the ball in each half second after it is released change in the way that it does?
Gravity pulling down on the ball, so it accelerates down at a steady rate
If an object falling freely were somehow equipped with an odometer to measure the distance it travels, then the amount of distance it travels each succeeding second would be
Greater than the second before
The distance a freely falling bowling ball falls each second
Increases
A speedometer normally measures
Instantaneous speed
What is the gain in speed per second for a freely falling object?
It gains about 10 m/s
As the angle of the inclined plane increases, hoe odes the final speed attained by the ball at the bottom of the inclined plane change?
It increases
How does the acceleration of the ball change as the angle of the inclined plane increases?
It increases
How does the distance traveled by the ball in the second half-second compare with the distance the ball traveled by the first half-second?
It increases
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
The distance of a freely falling object falls from rest on one-half second is
None of the above
While a car travels around a circular track at a constant speed, its
None of the above
The accelerations possible for a ball on an inclined plane
Range from zero to g
While an iron block near the Earth's surface is in free fall, it undergoes an increase in
Speed
Why does the final speed attained by the ball at the bottom of the inclined plane change in the way that it does when the angle of the incline plane increases?
The ball accelerates at a greater rate for the same duration of time
A ball is thrown upwards and returns to the same location. Compared with its initial speed its speed when it returns is about
The same
A rock dropped from a 5-m height accelerates at 10 m/s^2 and strikes the ground 1 s later. If the rock is dropped from a height of 2.5 m, its acceleration of fall is
The same
A ball rolling down an inclined plane each second picks up
The same amount of speed each second
If a car moves with a constant velocity, does it also move with a constant speed?
Yes, because constant velocity requires constant speed in the same direction
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
A cart maintains a constant velocity of 100 m/s for 10 seconds. During this interval its acceleration is
Zero
