Imagine you are Spiderman, and fall off a building from rest. After falling 10 m

Question

Imagine you are Spiderman, and fall off a building from rest. After falling 10 m, you shoot a sticky web straight up with a velocity relative to you of 20 m/s.

How fast are you moving when you shoot the sticky web?

A. -300 m/s

B. -196 m/s

C. -96 m/s

D. -14 m/s

Relative to the top of the building, what is the maximum height the sticky web will reach?

A. 18.6 m above

B. 8.16 m below

C. 10.4 m above

D. even with the roof

When will the sticky web return to you after you shoot it?

A. 2.1 s

B. 3.5 s

C. 19.2 s

D. never

Explanation / Answer

Use v2 = u2 + 2aH

=> v = - [0 + 2(9.8)(10)]1/2 = - 14 m/s

[option D].

So, velocity of the web with respect to the ground will be: 20 - 14 = 6 m/s

at the highest point, v = 0 m/s

so, h = [0 - 62]/(2)9.8 = 1.836m [upwards]

From the top, this will correspond to h' = 10 - 1.836 = 8.16 [downwards] [option B].

Since the acceleration is constant for both the bodies [acceleration due to gravity] therefore the web will never return to you after shooting since it had to travel upwards for an extra time while you were accelerating downwards.[option D].

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