A person has a choice while trying to push a crate across a horizontal pad of co

Question

A person has a choice while trying to push a crate across a horizontal pad of concrete: push it at a downward angle of 27degrees , or pull it at an upward angle 27degrees.

a)Which choice is most likely to require less force on the part of the person?
i)pushing or pulling shouldn't matter
ii)pushing at a downward angle
iii)pulling at the same angle, but upward

b)If the crate has a mass of 48.0kg and the coefficient of kinetic friction between it and the concrete is 0.800, calculate the required force to move it across the concrete at a steady speed for both situations.(both situations mean one to push one to pull).

Explanation / Answer

a)
3) as the normal will decreaese and hence the friction force will decrease
b)
in case of pulling
N=m*g-F*sin
frictional force=(m*g-F*sin)

F*cos=(m*g-F*sin)

.89*F/.8=480-.45*F

F=307.2N

in case of pushing

friction=(m*g+F*sin)

so F*cos=(m*g-F*sin)

.89*F/.8=480+.45*F

F=724.52N

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