4.) The following graph shows the position-vs-time for a car position m) 80 60 4

Question

4.) The following graph shows the position-vs-time for a car position m) 80 60 40 20 20 10 20 30 40 50 A) Explain the motion in your own words. B.) What is the velocity at 5 s? (6 m/s) C.) What is the velocity at 20 s? (-4 m/s) D.) What is the velocity at 12 s? (0 m/s) E) What is the average speed for the entire time? (3.64 m/s) F) Draw a v-vs-t graph neatly 5.) A rock is dropped from a cliff and falls for 5 s. a. Draw x-vs-t, v-vs-t and a -vs-t graphs. Use the graphs to solve the following b. How far did the rock fall in 3 s? (45 m) c. ow fast was the rock falling at 4 s? (-40 m/s) d. How far did the rock fall between 2 and 3 s? (25 m) 6.) The same rock is dropped from a cliff and falls 85 m before hitting the ground a. How fast did the rock hit the ground? (41.2 m/s) b. How long did it take the rock to fal? (4.12 s) c. What was the acceleration at 3 s? (-10 m/s)

Explanation / Answer

A] In the first segment, the velocity of the motion is positive and constant until t = 10s.

From t=10s to t=15s, the object comes to rest (zero velocity). From t=15s to t=40s, the object changes the direction of motion (negative velocity). Finally, from t=40s to t=55s, the object changes its direction of motion (positive velocity).

B] velocity at t=5s is the slope of the x-t graph

v = (60 - 0)/(10-0) = 6 m/s

C] velocity at t=20s is:

v = (0-60)/(30-15) = - 4 m/s

D] Since the object is at rest from t=15s to t=20s, at t=12s, the velocity is zero. v = 0 m/s.

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