The girl's brother stands at the edge of the Golden Gate Bridge and throws a penny upwards at 29 m/s at an angle of 34°. How long does it take the penny to fall to the water, 227m below? How far from the base of the bridge does the penny hit the water?

1 Answer
Sep 21, 2015

Total time of flight is 8,66 s, and range of projectile is 2082 m.

Explanation:

I will break the projectile motion of the penny up into different stages :
A: Release
B : Max height
C: Release height.
D: Water.
In addition, I will consider horizontal (X) and vertical (Y) directions separately for each stage.
The X-Direction:
In the x-direction, there is no acceleration and hence constant velocity of #29cos34^@=24,042m//s#
The Y-Direction:
In the y-direction, there is constant acceleration throughout due to gravity of value #g=-9,8m//s^2#

Now we get:

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Maximum height is reached at point B, so working from A - B in the y-direction we get #s=ut+1/2at^2 =13,417m#
Hence the maximum height above the water is #227+13,417=240,417m#

Since it reaches its maximum height after 1,655s, its horizontal range at this time in the x-direction is #s_x =vcosθ⋅t=39,79m#

Thus, by Pythagoras, the distance from the bridge at this point is #sqrt(39,79^2 +13.417^2)=42m#