physics test 2 conceptual
What would really happen in Alice in wonder land if she tries to grab the jar and dropped it, describe its motion
Alice would not see any motion of the jar relative to her. Someone sitting on a shelf would see the jar in free fall
Why is it not correct to claim that "matter can neither be created nor destroyed"?
Matter and energy can be converted to each other.
You are on a spaceship somewhere in the galaxy. Could you devise an experiment to determine your speed?
Because the physical laws are the same in all inertial systems, it is impossible to determine your speed.
A bowler picks up a bowling ball from the floor and puts it on a rack. If you know the balls weight, what else must you know to calculate the work done?
Because work is the force in the direction of motion times the distance moved, we must know how high she lifted the ball.
Who has the greater rotational speed, a person at the equator or one living in New York?
Both locations make one complete rotation every day, so they have the same rotational speed.
Two Forces are used to move a block 2 meters across a level surface as shown. Is the work done by force A greater than, equal to or less than force B ?
Force A does equal work because the component of the force in the direction of the displacement is the same.
s it better to analyze a collision between two cars using conservation of momentum or conservation of kinetic energy?
Momentum is always conserved in a collision whereas kinetic energy is rarely conserved.
According to the special theory of relativity, a twin that takes a long trip at high speed can return to earth at a younger age than his twin who remained at home. Could the traveling twin ever return home before his brother was born?
No, the special theory of relativity does not allow one to travel backward in time.
A figure skater spins with her arms straight out. Which has greater rotational speed, her fingertips or her shoulders?
Rotational speed describes that rate at which revolutions are completed. It is the same for all points on a rotating body.
The conductor of a high speed train uses a meter stick to measure the length of her train at 200 m while the train is stopped at the station. The train then travels at 80% of the speed of light. If she repeats the measurement on the moving train, what answer would she get?
Since the train and ruler are both moving, she will still get 200 m.
if the train is moving to the right and the acceleration is to the right, is it speeding up and slowing down? what if it is moving to the left
The acceleration points to the right. If the velocity is to the right, the train is speeding up. If the velocity is to the left, the train is slowing down.
A flywheel with a large rotational inertia is attached to the driveshaft of automobile engines. What is its purpose?
The flywheel smooth's the rotational motion of the engine because of its rotational inertia.
An airplane is flying due south and gets hit with a wind going north. Will the kinetic energy increase or decrease?
The kinetic energy decreases because the force and the displacement are in opposite directions.
Why do figure skaters spin faster when they pull their arms in?
The lower rotational inertia produced by pulling in the arms requires a larger rotational speed to conserve angular momentum
Your friend is driving her 1964 Thunderbird convertible straight towards you at 40 mph. She stands up and throws a baseball forward at 30 mph. How fast do you see the ball approaching you?
You see the ball approaching at 70 mph.
Newtons first law states that every object remains at rest or in motion in a straight line at constant speed unless acted on by an unbalanced force. Is this law true in all reference frames?
no. Newtons first law is only true in inertial reference frames, and defines only such frames
