Show:
The Fab Five
Free Falling
Experimental
Pot Luck
100
What two conditions must be met before you can use the three equations we derived in this module?
Motion must be in a straight line, and acceleration must be constant.
100
What is the definition of free fall?
The motion of an object when it is falling solely under the influence of gravity.
100
In Experiment 2.1, what did we learn about gravity?
The acceleration due to gravity is the same for all objects, but due to air resistance, some things fall more slowly.
100
What is air resistance and what causes it?
Air resistance reduces the acceleration of objects that are falling. The object that falls must shove air molecules and atoms out of the way in order to fall. (correct answer should mention that it reduces acceleration, and that it's due to air molecules).
200
Why do we need five equations for motion instead of just one?
We have several variables involved in motion and we need to be able to relate the ones that are in the problem. We won't always know all of the variables.
200
A very picky physicist says that no object can really experience free fall when falling near the surface of the earth. Explain why the physicist is technically correct.
Since all objects falling near the surface of the earth are in air, they all experience air resistance, which means they are not falling solely under the influence of gravity.
200
In Experiment 2.1, under what conditions did the paper and the book fall at the same rate?
When the paper was on top of the book.
200
If an object is thrown up in the air, where is its velocity zero?
Velocity is zero at the maximum height.
300
Which equation would we use if we know velocity, acceleration, and displacement; and we want to find the initial velocity?
Equation 2.15 (v^2 = vo^2 + 2 a dx)
300
In an amusement park, there is a free fall ride that drops riders straight down for 30.0 m. What velocity is the ride traveling at when it reaches the bottom of this straight drop?
24 m/sec down.
300
In Experiment 2.2, how did you measure your subject's reaction time?
By measuring the distance that the ruler fell and calculating the time.
300
A ball is thrown up in the air with an initial velocity of 1.2 m/sec. If the ball is caught at exactly the same height from which it was thrown, what will its velocity be?
-1.2 m/sec (don't forget the - sign or "down")
400
An athlete runs at a constant velocity of 3.0 m/s. How far will the athlete travel in 25 minutes?
4.5E3 meters
400
A physics student drops a rock off of a cliff. If the rock takes 3.5 seconds to reach the bottom of the cliff, how tall is the cliff (in meters)?
6.0E1 (60) meters high
400
In Experiment 2.3, what three things were found to affect air resistance?
Weight, shape, and orientation.
400
A child throws a ball up in the air with an initial velocity of 3.9 m/sec. What is the maximum height that the ball reaches?
0.78 meters
500
A car, traveling at 25 m/sec, stops in 0.103 km. What is the deceleration provided by the brakes?
-3.0 m/sec^2 (don't forget the - sign).
500
A physics student stands on a ladder 12 feet above the ground and throws a ball up into the air. If it takes the ball 4.2 seconds to hit the ground, what was the ball's initial velocity?
64 ft/sec up (don't forget the direction)
500
In Experiment 2.2, assume you measured a drop distance of 12 cm. What was the subject's reaction time?
0.16 seconds.
500
A parachutist falls from a plane for 5.0 seconds before opening the parachute. How fast is he traveling when he opens his parachute?
49 m/sec (100 mph)