Bob has just finished climbing a sheer cliff above a beach and wants to figure o
ID: 2127991 • Letter: B
Question
Bob has just finished climbing a sheer cliff above a beach and wants to figure out hociw high he climbed all he has to use, however is a baseball, a stopwatch and a friend on the ground below with a ling measuring tape. Bob is a picher, and knows that the fastest he can throw the ball is about 31.7 m/s. Bob starts the stopwatch as he throws the ball (no way to measure balls initial trajectory), and watches carefully. The ball rises and then falls and after 0.710 seconds tha ball is once again level with Bob. Bob can't see well enough to time when the all hits the ground. Bobs friend then measures that the ball lands 126m from the base of the cliff. How high up is bob if the ball started from exactly 2 m above the edge of the cliff
Explanation / Answer
when ball comes to level of bob :
0 = 31.7sinA x 0.710 - g x 0.710^2/2
sinA = 6.3 degrees.
t = 126 / 31.7cos6.3 = 4 sec .
H = 31.7sin6.3 x 4 - 9.81 x 4^2/2 = - 64.46 m
height = 64.46m