Physics: Chapter 3
A ball freely falling at 20 m/s will in the next second have a speed of _______.
30 m/s
scalar quantity
a quantity that has only a magnitude, not a direction
Disregarding air resistance, objects fall with constant
acceleration.
In its first second of free fall, a dropped softball will fall a vertical distance of _______.
5 m
Calculate the average speed of a cheetah that runs 150 meters in 6.0 seconds.
Vave = 25 ms
velocity
an object's speed and direction of motion
If an object moves with constant acceleration, its velocity must
change by the same amount each second.
In each second of fall, the distance a freely falling object will fall is
increasing.
A speedometer normally measures _______.
instantaneous speed
While an object near the Earth's surface is in free fall, its
velocity increases
free fall
motion under the influence of gravity only
An apple drops from a tree and hits the ground in 1.6s . Calculate how far it falls.
s = 13 m
instantaneous speed
the speed at any instant
average speed
the total distance traveled divided by the time of travel
What is the instantaneous velocity of a freely falling object 14s after it is released from a position of rest?
v = -140 ms
A hockey puck is set in motion across a frozen pond. If ice friction and air resistance are neglected, the force required to keep the puck sliding at constant velocity is
zero.
A car accelerates at 2 meters/s/s. Assuming the car starts from rest, how far will it travel in 10 s?
100 m
speed
how fast an object moves; the distance traveled per unit of time
If a freely falling object were somehow equipped with a speedometer, its speed reading would increase each second by about
10 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 in meters per second per second is approximately
0.
If a projectile is fired straight up at a speed of 10 m/s, the time it takes to reach the top of its path is about
1 second.
vector quantity
a quantity that has magnitude and direction
It takes 6 seconds for a stone to fall to the bottom of a mine shaft. How deep is the shaft?
about 180 m
Galileo discovered that when air resistance can be neglected, all objects fall with the same _______.
acceleration
Calculate the vertical distance an object dropped from rest covers in 14s of free fall.
d = 980 m
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
A bullet is dropped from the top of the Empire State Building while another bullet is fired downward from the same location. Neglecting air resistance, the acceleration of
each bullet is 9.8 meters per second per second.
Calculate the distance (in km) that Larry runs if he maintains an average speed of 9.3km/h for 1 hour.
s = 9.3 km
A ball is thrown upwards and returns to the same position. Compared with its original speed after release, its speed when it returns is about
the same.
What is its average velocity during this 14-s interval?
v = -69 ms
An object is dropped from rest and falls freely. After 7.8s , calculate its instantaneous speed.
v = 78 ms
Calculate your walking speed when you step 1.0 meter in 0.55 second.
v = 1.8 ms
A car maintains a constant velocity of 100 km/hr for 10 seconds. During this interval its acceleration is
zero.
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.
acceleration
the rate at which velocity changes with time; the change in velocity may be in magnitude, or direction or both
When a rock thrown straight upwards gets to the exact top of its path, its
velocity is zero and its acceleration is about 10 meters per second per second.
An object falls freely from rest on a planet where the acceleration due to gravity is 20 meters per second squared. After 5 seconds, the object will have a speed of
100 m/s.
While you're in a bus that moves at 100 km/h, you walk from the back to the front at 10 km/h. What is your speed relative to the road outside?
110 km/h
If a projectile is fired straight up at a speed of 10 m/s, the total time to return to its starting position is about
2 seconds.
A horse gallops a distance of 10 kilometers in a time of 30 minutes. Its average speed is
20 km/h
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 somehow equipped with a speedometer on a planet where the acceleration due to gravity is 20 m/s/s, then its speed reading would increase each second by
20 m/s.
At one instant a heavy object in air is moving upward at 50 meters per second. One second later its speed is approximately
40 m/s.
One half second after starting from rest, a freely falling object will have a speed of about
5 m/s.
If a car accelerates from rest at 2 meters per second per second, its speed 3 seconds later will be about
6 m/s.
If you drop an object, it will accelerate downward at a rate of 9.8 meters per second per second. If you instead throw it downwards, its acceleration (in the absence of air resistance) will be
9.8 meters per second per second.
