physics ch10
What exactly is a projectile?
An object that is projected by some means and continues in motion by its own inertia.
The crew of a cargo plane wishes to drop a crate of supplies on a target below. To hit the target, when should the crew drop the crate? Ignore air resistance.
Before the plane is directly over the target
When Dr. Hewitt releases the two projectiles, which one hits the ground first?
Both balls hit the ground at the same time.
Why do the two objects hit the table at the relative times that they do?
Gravity pulls the same amount on each ball, and they each drop the same distance.
Predict how the vertical component of the velocity will change with time after the projectile is fired.
It first decreases to zero and then increases in the opposite direction.
Predict how the horizontal component of the velocity will change with time after the projectile is fired.
It stays constant
Which ball (if either) has the greatest speed at the moment of impact?
The ball thrown horizontally
Consider the video demonstration that you just watched. A more complete explanation of what you saw will be possible after covering Newton's laws. For now, consider the following question: How would the result of this experiment change if we replaced the ball with another one that had half the mass? Ignore air resistance.
The ball would still land in the cart.
Which projectile spends more time in the air, the one fired from 30∘∘ or the one fired from 60∘∘?
The one fired from 60∘
What did Kepler discover about the periods of planets and their distances from the Sun?
The period squared was proportional to the distance cubed.
A ball is thrown horizontally from a cliff at a speed of 10 m/sm/s . You predict that its speed 1 ss later will be slightly greater than 14 m/sm/s . Your friend says it will be 10 m/sm/s. Who is correct?
You
Kepler was the first to be credited for discovering that planets follow __________.
elliptical paths
Consider the video you just watched. Suppose we replace the original launcher with one that fires the ball upward at twice the speed. We make no other changes. How far behind the cart will the ball land, compared to the distance in the original experiment?
four times as far
