Problem 2.71 Astone is thrown vertically upward with a speed of 13.5 m/s from th

Question

Problem 2.71 Astone is thrown vertically upward with a speed of 13.5 m/s from the edge of a clit 75.0 m high (Elgute 1) Figure 1 Part A How much later does it reach the bomom of the dm Express your answer to three significant figures and include the appropriate units. Value s Mr Answers Incorrect: Try Again: 4 attempts remaining Part B What is its speed ust before hitting? Express your answer to three significant fig ures and include the appropriate units. Co Value m Subm My Answers Give Up 12 20 next

Explanation / Answer

here,

initial speed , u = 13.5 m/s

height of cliff , h0 = 75 m

A)

let the time taken be t

h0 = - u * t + 0.5 * g * t^2

75 = - 13.5 * t + 4.9 * t^2

solving for t

t = 5.53 s

the time taken is 5.53 s

B)

the speed before hiting be v

v^2 - u^2 = 2 * g * h

v^2 - 13.5^2 = 2 * 9.8 * 75

v = 40.65 m/s

the final speed is 40.65 m/s

C)

let the maximum height reached be hmax

hmax = u^2 /2g

hmax = 13.5^2 /(2 * 9.8)

hmax = 9.3 m

the total distance travelled , d = 2 * hmax + h0

d = 2 * 9.3 + 75 = 93.6 m

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