Question

34. A girl is standing on the top edge of an 18 m high building. She tosses a coin upward with a speed of
7.0 ms !. How long does it take for the coin to hit the ground ? How fast is the coin going just before
it strikes the ground ? (g = 10 ms)
1) 2.70s, 20 m/s 2) 1.70s, 30 m/s 3) 4.70s,50m/s 4)10s,50m/s
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Answer 1

Answer:

1

See Attachment

Thanks for Reading

Answer 2

It takes 2.7 seconds for the coin to hit the ground, and its velocity just above the ground is 20m/s. (option 1)

Given,

The height of the building, h = 18 m.

Initial velocity, u = 7 m/s.

To find,

The time taken to hit the ground, t.

The final velocity of the coin, v.

Solution,

Using the equation of motion for accelerated motion,

$v^2 = u^2 +2gh$

⇒ v = √(49+2×10×18)

⇒ v = √409 ≈ 20 m/s

also,

v = u + at

⇒ 20 = -7 + 10t

⇒ t = 2.7s

Hence we can conclude that its takes 2.7s for the coin to hit the ground and its velocity just above the ground is 20 m.

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