Lesson 5 - Free Fall

In a vacuum tube, a feather is seen to fall as fast as a coin. This is because

• gravity doesn’t act in a vacuum

• air resistance doesn’t act in a vacuum

• greater air resistance acts on the coin

• gravity is greater in a vacuum

Without air resistance, the time for a vertically tossed ball to return to where it was thrown is

• 10 m/s for every second in the air

• the same as the time going upward

• less than the time going upward

• more than the time going upward

A kangaroo is capable to a height of 2.62 m. Determine the takeoff speed of the kangaroo.

• 2.62 m/s

• 9.8 m/s

• 7.17 m/s

• 51.35 m/s

A rock falls 180 m from a cliff into the ocean. How long is it in free fall?

• 6 s

• 10 s

• 18 s

• 180 s

A ball is projected upward with an initial speed of approximately 50 m/s. The diagram below represents its position at 1-second intervals of time. At what location will the ball be moving downward with a speed of approximately 10 m/s?

• I

• G

• E

• D

Which speed vs time curve has the right shape for free fall when air resistance can be neglected?

• 1

• 2

• 3

• 4

Which of the following statements applies to the motion of a ball rising and then falling in free fall?

I. The ball has constant velocity as it moves upward.

II. The ball has constant acceleration at the top of its path.

III. The ball has constant acceleration as it moves downward.

IV. The ball has zero velocity at its maximum height.

• II, III and IV only

• I and III

• I and II only

• I, II and III

A ball is thrown upward in the air with an initial velocity of 40 m/s. How long does it take to reach back to the point it was thrown from?

• 4 s

• 6 s

• 2 s

• 8 s

How does the Vi compare to the Vf in a free fall problem?

• Vi and Vf are exactly the same, this is because of symmetry

• Vi and Vf are the same in magnitude, but different in vector

• Vi and Vf are close but Vf is larger because you would fall faster than you would rise, since you are slowing down

• Since the object must start at 0 m/s and end at 0 m/s, Vi and Vf are the same

If a free falling object takes 10s to travel upward, what is the total time the object is in the air?

• 0 s because of symmetry and T_up = +10s, so T_down = -10s. Which means that T_total = 0s.

• Greater than 10 s, but less than 20 s because the object would fall faster than it rose because of gravity. Without more information, you cannot calculate this number.

• 20s because of symmetry and T_up = 10s, so T_down = 10s. Which means that T_total = 20s.

• Less than 10s because the object begins falling back before the 10s and it falls faster than it rises.