Question

a ball is dropped from a height of 100 inches the ball bounces, each time reaching a lower and lower height. the height of each bounce is 75% of the previous bounce what height will the ball reach after bouncing four time? how many bounces does it take for the ball to reach a heigh of less than one inch?

Answer 1

After the 'n'th bounce, the ball returns to a maximum height of

(100) times (0.75)^n .

-- After 4 bounces, the maximum height is (100) (0.75)^4 = 31.64 inches.

-- To look for the maximum height of 1 inch, (100) (0.75)^x = 1

Let's take the log of each side: log(100) + x log(0.75) = 0

Subtract log(100) from each side: x log(0.75) = -log(100)

Divide each side by log(0.75) : x = -log(100) / log(0.75).

log(100) = 2 . So ... x = -2 / log(0.75) = -2 / -0.124939 = 16.00785

So the ball returns to a slim hair more than 1 inch high on the 16th bounce,
and returns to definitely less than 1 inch high on the 17th bounce.