# physics!

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A student is about to do a push-up. Her
center of gravity lies directly above P on the
ﬂoor, which is 1.1 m from her feet and 0.4 m
from her hands.
If her mass is 55 kg, what is the force exerted by the ﬂoor on her hands? The acceleration of gravity is 9.81 m/s
2
.

• physics! -

While stationary, the total moment about an axis through her toes is zero.

Her hands are 1.5 m from her toes. Her center of mass is 1.1 m from her toes.

F*1.5 - M*g*1.1 = 0

F = (1.1/1.5)M*g = 395 Newtons

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