#8 #16 #20 #26 8. If an airplane averages 550 mph, how far can it fly in 4 hours?
16. What average acceleration does it take to stop a car traveling at 56 mph in 8 s?
20. A window washer drops a bucket of water. If it hits the ground traveling at 54 m/s, how fast was it moving 1 s earlier? Two seconds earlier?
Since the acceleration of gravity is 10 m/s/s DOWN, the speed of an object traveling DOWN increases by 10 m/s every second. The bucket hit the ground at 54 m/s DOWN. One second earlier it was moving at 44 m/s DOWN, that is 10 m/s less than the final 54 m/s. And, two seconds before the bucket hit the ground it was traveling 34 m/s DOWN. Therefore, the speed of the bucket was 44 m/s one second before impact and 34 m/s two seconds before impact.
An Alternate Method26. While standing on the edge of a cliff, a baseball player throws a ball vertically upward with a speed of 20 m/s. If the ball remains in the air for 6 s, what is the height of the cliff?
Let's use the table method that we did together in class. Begin by filling in the information given in the problem (in black on green entries). Then, fill in the table like we did in class using the numbers given in this problem (the red on yellow entries).
Since the ground is 60 m below the cliff, the cliff is 60 m high.