A robot standing at the bottom of cliff shoots a ball upwards .The ball reaches max height of 80m in 4s .what is the height of the cliff if it reaches the top of the cliff 7s after the shoot?
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Given:
A robot standing at the bottom of cliff shoots a ball upwards. The ball reaches max height of 80m in 4s .
To find:
What is the height of the cliff if it reaches the top of the cliff 7s after the shoot?
Solution:
From given, we have,
The ball reaches max height of 80m in 4s.
we use the formula,
S = 1/2(u + v)t
80 = 1/2(u + 0)4
160 = 4u
u = 40 m/s
Magnitude of acceleration due to gravity,
a = |(v - u) /t|= |(0 - 40)/4| = 10 m/s^2
Based on the given data, we have obtained a = 10 m/s^2
Distance moved from top to cliff be = x
S = ut + (1/2)at^2
x =0 × (7 - 4) + (1/2) × 10 × (7 - 4)^2
x = 0 + 5(9)
x = 45 m
Height of cliff = 80 m - 45 m = 35 m
Therefore, the height of the cliff is 35 m.
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