PHY Ch. 3
An object falls freely from rest on a planet where the acceleration due to gravity is 20 meters per second squared. In the first 5 seconds it falls a distance of
250 m
One half second after starting from rest, a freely-falling object will have a speed of about
5 m/s.
A ball is thrown 125 meters upward and then falls the same distance back to Earth. Neglecting air resistance, its total time in the air is about
5 seconds.
How fast an object is moving, and in what direction.
Velocity
A heavy object and a light object are dropped at the same time from rest in a vacuum. The heavier object reaches the ground
at the same time as the lighter object
Consider drops of water that leak from a dripping faucet. As the drops fall they
get further apart
A ball is thrown upwards and caught when it comes back down. In the presence of air resistance, the speed with which it is caught is
less than the speed it had when thrown upwards
What is the acceleration of a car that maintains a constant velocity of 100 km/hr for 10 seconds?
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 m/s
At one instant an object in free fall is moving downward at 50 meters per second. One second later its speed is about
60 m/s
. It takes 6 seconds for a stone to fall to the bottom of a mine shaft. How deep is the shaft?
about 180 m
The rate at which velocity is changing with time.
acceleration
Galileo used inclined planes to ____ the effective acceleration (of a rolling cylinder or ball) compared to earth's gravity
decrease
Galileo's use of inclined planes allowed him to effectively
slow down the acceleration of free fall.
How fast an object is moving, without consideration of direction
speed
In each second of fall, the distance a freely falling object will fall is
Increasing
A base ball is hit straight up into the air at a speed of 20 m/s. How long does it take to reach the high-point in its trajectory.
2 seconds
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 baseball is hit vertically upward at 30 m/s. One second later its speed is about ____ vertically upward.
20 m/s
A freely falling object started from rest. 2 seconds later, its speed is about
20 m/s
If an object falling freely downward were somehow equipped with a speedometer on a planet where the acceleration due to gravity is 20 meters per second per second, then its speed reading would increase each second by
20 m/s
An object is falling under the influence of gravity, and with no air-resistance.
Free fall
If an object falling freely downward 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
A ball is thrown upwards and caught once it comes back down. The speed of the ball as it returns and is caught is ___ if there is air resistance compared to if there were no air resistance.
lower
