G A3.2 - Cliff Problems

Get the Assessment: FA03.2.pdf

This assessment covers the following video flips:

3F. Understand the basic idea behind projectile motion.
3G. Solve Cliff Problems.

The Assessment Solved:

A ball rolls off the edge of a 15.0 m tall cliff with a purely horizontal velocity, and strikes the ground at a distance of 12.4 m from the base of the cliff.

1. What time was the ball in the air? (1.75 s)

2. What was the ball’s horizontal velocity? (7.09 m/s)

3. What is the final vertical velocity?

(Just before it hits the ground) (-17.1 m/s)

4-5: Draw a picture of the final velocity of impact. Calculate the speed it is traveling, and find the angle below horizontal the velocity makes.

(speed = 18.6 m/s, 67.5o below horiz.)

1-5. Watch the video and make sure you have drawn the velocity correctly.

Example 2.

Example 3.

Help with the Quizlette:

<Video #1> 1. Red Elk runs at a speed of 9.20 m/s horizontally off a cliff that is 6.40 m above the water.

<Video #2> 2. Red Elk runs with a purely horizontal velocity and lands 8.50 m from the base of the cliff 1.20 seconds later.

<Video #3> 3. Red Elk runs with a purely horizontal velocity of 5.60 m/s and hits the water 1.80 seconds later.

<Video #4> 4. Red Elk runs with a purely horizontal velocity of 4.30 m/s and lands 5.10 m from the base of the cliff .

<Video #5> 5. Red Elk runs with a purely horizontal velocity and lands 8.60 m from the base of a 13.0 m tall cliff.

More Practice Problems:

Ignore air friction and use the convention that down is negative. g = 9.80 m/s/s

1. A ball is projected with a purely horizontal velocity from an 7.60 m tall cliff and lands 11.3 m from the base of the cliff.

a. What time is the ball in the air?

b. With what purely horizontal velocity was it projected from the top of the cliff?

c. What is the final vertical velocity? (Just before it hits the ground)