Answer:
The answer is vc=-0.645m/s
Explanation:
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Let's solve this!
First we will write down the data:
mc (child's mass): 61kg
mr (rock mass): 4kg
vr (rock speed): 12m / s
angle: 35 °
We will calculate the velocity in x of the rock:
vxr = 12m / s * cos (35 °) = 9.83m / s
mc * vc + mr * vrx = 0
We cleared vc that is the incognita
vc = -mr * vrx / mc
vc = (4kg * 9.83m / s) / 61kg
vc = -0.645m / s
The speed of the person is 0.645 m / s. It is negative because the direction in which the person moves is contrary to the direction to which the rock throws.
The answer is vc=-0.645m/s