Question

Q5 A rock is dropped off a cliff 115 m high. How long does it take for the rock to
reach the ground?​

Answer 1

Given,

Height (h) = 115 m

Acceleration due to gravity (g) = 9.8 m/s²

Initial Velocity (u) = 0 m/s

∴ h = ut+0.5gt²

115 = 0.5*9.8*t²

115 = 4.9t²

23.46 = t²

4.84 seconds = t

It will take a time of 4.84 seconds to reach the ground.

I hope this helps.

Answer 2

Time Taken By The Rock To Reach The Ground Is 4.83 Sec

GIVEN

Height of the cliff = 115 m

To Find

Time is taken by the rock to reach the ground.

SOLUTION

Height of the cliff = 115.

we know that,

Acceleration due to gravity(g) = 9.8 m/s²

the initial velocity of the rock, u = 0 m/s

Applying the second equation of motion

$S = ut + \frac{1}{2} g {t}^{2}$

where,

s = height of the cliff

u = initial velocity

t = time taken

g = acceleration due to gravity

putting the values in the above equation -

$115 = 0 \times t + \frac{1}{2} 9.8 \times {t}^{2}$

${t}^{2} = 23.4$

$t = \sqrt{23.4}$

t = 4.83

Hence, The Time Taken By The Rock To Reach The Ground Is 4.83 Sec

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