Throwing Stones Two stones are launched from the top of a tall building. One sto

Question

Throwing Stones

Two stones are launched from the top of a tall building. One stone is thrown in a direction 25.0 above the horizontal with a speed of 20.0 m/s ; the other is thrown in a direction 25.0 below the horizontal with the same speed.

Part A

Which stone spends more time in the air? (Neglect air resistance.)

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Part B

This question will be shown after you complete previous question(s).

Throwing Stones

Two stones are launched from the top of a tall building. One stone is thrown in a direction 25.0 above the horizontal with a speed of 20.0 m/s ; the other is thrown in a direction 25.0 below the horizontal with the same speed.

Part A

Which stone spends more time in the air? (Neglect air resistance.)

Which stone spends more time in the air? (Neglect air resistance.)

SubmitHintsMy AnswersGive UpReview Part

Part B

This question will be shown after you complete previous question(s).

The stone thrown upward spends more time in the air. The stone thrown downward spends more time in the air. Both stones spend the same amount of time in the air.

Explanation / Answer

Both stones have equal and opposite initial velocity. Let u and -u be the their initial speeds. Let t1 and t2 be the time taken by stones thrown upwards and downwards respectively. Also let 'd' be the height of the building.

Then,

For stone thrown upwards,

-d = ut1 -gt12/2

For stone thrown downwards,

-d = -ut2 - gt22/2

Eliminating d from these equations, we get,

ut1 -gt12/2 = -ut2 - gt22/2

=> g(t12 - t22)/2 = 2u(t1 + t2)

=> t12 - t22 > 0

=> t1 > t2

So, the stone thrown upwards will spend more time in the air.

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