Answer:
99.2 N
Explanation:
To solve the problem, we have to write the equation of the forces along two perpendicular directions.
Along the vertical direction:
(1)
where
N is the normal reaction of the floor on the crate
F is the force applied by the worker
is the angle at which the force is applied
mg is the weight of the crate, with
m = 30.0 kg (mass of the crate)
(acceleration of gravity)
Along the horizontal direction:
where
is the force of friction, where
is the coefficient of friction
and
a is the acceleration; since the crate is moving at constant velocity, the acceleration is zero, so
And the equation becomes
(2)
From eq.(1) we get:
And substituting into (2) we get