In the middle of the night you are standing a horizontal distance of 14.0 m from

Question

In the middle of the night you are standing a horizontal distance of 14.0 m from the high fence that surrounds the estate of your rich uncle. The top of the fence is 5.00 m above the ground. You have taped an important message to a rock that you want to throw over the fence. The ground is level, and the width of the fence is small enough to be ignored. You throw the rock from a height of 1.60 m above the ground and at an angle of 40.0 above the horizontal.

A) What minimum initial speed must the rock have as it leaves your hand to clear the top of the fence?

Explanation / Answer

here,

height of fence , h = 5 m

height of rock , hi = 1.6 m

theta = 40 degree

height covered by rock , h' = h - hi

h' = 3.4 m

let the minimum initial speed be u

- 2 * g * h' = 0 - ( u * sin(theta))^2

2 * 9.8 * 3.4^2 = - ( u * sin(40))^2

u = 23.42 m/s

the minimum speed o fthe rock when it leaves the hand is 23.43 m/s

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