7. a roller coaster’s velocity at the top of a hill is 10 m/s. two seconds later it reaches the bottom ofthe hill with a velocity of 26 m/s. what was the acceleration of the coaster? 8. a roller coaster is moving at 25 m/s at the bottom of a hill. three seconds later it reaches the top ofthe hill moving at 10 m/s. what was the acceleration of the coaster? 9. a car traveling at 15 m/s starts to decelerate steadily. it comes to a complete stop in 10 seconds. what is it’s acceleration? 10. a child drops a ball from a window. the ball strikes the ground in 3.0 seconds. what is thevelocity of the ball the instant before it hits the ground?

7)

8)

9)

10)

Explanation:

For the problems 7, 8 and 9 we just apply the definition of acceleration, since no more information is given, which is:

So for each problem we will have:

7)

8)

9)

For the problem 10, we use the equation of velocity in accelerated motion:

Since the ball starts from rest and the acceleration is that of gravity (we take the downward direction positive), we have:

because it says use -2,0,and 2 for x, we can plug those numbers into the equation. y/4=3/4(-2)+2   y/4= -1 1/2 +2 now to get x by itself, we can multiply each side by 4. y=-6+8 which equals y=2 when x=-2. now you can do the same thing with 0 and 2 as x. you get y=8 when x=0 and y=14 when x=2.

x   |   y

-2 |   2

0   |   8

2   |   14