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47. (a) Calculate the height of a cliff if it takes 2.35 s for a rock to hit the ground when it is thrown straight up

from the cliff with an initial velocity of 8.00 m/s. (b) How long would it take to reach the ground if it is thrown
straight down with the same speed?

1 Answer

4 votes

Answer:

Step-by-step explanation:

A) The height of the cliff is calculated to be 18.8 meters.

B) It would take 1.63 seconds to reach the ground when thrown straight down.

Given that,

A) To calculate the height of the cliff:

Initial velocity (vi): 8.00 m/s

Time taken (t): 2.35 s

B) To calculate the time it takes to reach the ground when thrown straight down:

Initial velocity (vi): 8.00 m/s

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

A) To calculate the height of the cliff,

Use the equation of motion:

h = (vi t) + (0.5 g t²),

Where h is the height,

vi is the initial velocity,

t is the time,

g is the acceleration due to gravity.

Plugging in the given values, we have

h = (8.00 x 2.35 ) + (0.5x9.8(2.35 s)²).

By solving this equation, the height of the cliff = 18.8 m

B) If the rock is thrown straight down at the same speed,

Calculate the time it takes to reach the ground using the equation:

t = (2 vi) / g,

Where,

t is the time,

vi is the initial velocity,

g is the acceleration due to gravity.

Plugging in the given values, we have

t = (2x8.00) /9.8

By solving this equation,

The time it takes to reach the ground = 1.63 second

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