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**1. Homework Statement**

While rolling balls down an inclined plane, Galileo observes that the ball rolls 1 cubit (the distance from elbow to fingertip) as he counts to 10. How far will the ball have rolled from its starting point when he has counted to 20?

The answer I get is supposed to be 4 cubits

2. Homework Equations

2. Homework Equations

d = 1/2 a t^2

**3. The Attempt at a Solution**

Ball is rolling at 1 cubit / 10 count.

t = 20 count = two 10counts = 2t

d = 1/2 a t^2

d = 1/2 a (2t)^2

d = 1/2 * 4t^2 * a

2d = 4t^2 * a

I don't know where to go from here

**1. Homework Statement**Someone standing at the edge of a cliff (as in the following figure) throws a ball nearly straight up at a certain speed and another ball nearly straight down with the same initial speed. If air resistance is negligible, which ball will have the greater speed when it strikes the ground below?

This time I do not know what the correct answer will be

**2. Homework Equations**None, theory problem

**3. The Attempt at a Solution**I think that the ball thrown up will have a greater acceleration because it will fall from a higher point (once it reaches that highest point). So it will have a longer time to accelerate.

**1. Homework Statement**A freely falling object falls 5.0s after it is released from a position of rest. How far will it fall in this time?

Express your answer to two significant figures and include the appropriate units.

**2. Homework Equations**d = 1/2 a t^2

**3. The Attempt at a Solution**a = g = -10m/s^2

t = 5s

d = 1/2 (-10m/s^2) (5s)^2

d = -5m/s^2 (25s^2)

d = -125m

want distance fallen so take absolute value of d = -125

d = 125m

But it tells me that I am wrong. :(