A 40 N box is pushed 5 m up a ramp. The angle of the ramp is 37° above the horizontal. The applied force is parallel to the ramp and opposed by a frictional force of 10.0 N. Find the net increase in potential energy by the crate.

Respuesta :

The net increase in potential energy by the crate is negative 49.4 Joules. That is, ΔP.E = - 49.4 J

Given that a 40N box is pushed 5 m up a ramp. The angle of the ramp is 37° above the horizontal.

We can find the height h of the ramp with the equation below;

h = 5sin 37

h = 3.009 m

Mass of the box = 40/9.8 = 4.082 kg

The maximum energy attained = mgh

Maximum Energy = 4.082 x 9.8 x 3.009

E = 120.36 J

The maximum K.E = Maximum P.E

1/2m[tex]U^{2}[/tex] = 120.36

m[tex]U^{2}[/tex] = 240.72

[tex]U^{2}[/tex] = 240.72 / 4.082

[tex]U^{2}[/tex] = 58.97

U = [tex]\sqrt{58.97}[/tex]

U = 7.7 m/s

We can find the acceleration by using third equation of motion

[tex]V^{2}[/tex] = [tex]U^{2}[/tex] - 2aS

Since the box is going to rest, V = 0, and acceleration will be negative

0 = 7.7^2 - 2 x a x 5

10a = 59.29

a = 59.29/10

a = 5.93 m/[tex]s^{2}[/tex]s^2

The applied force F = ma

F = 4.082 x 5.93

F = 24.2 N

Given also that the applied force is parallel to the ramp and opposed by a frictional force of 10.0 N. The net increase in potential energy by the crate will be

ΔP.E = Net work done

ΔP.E = Net force x distance

ΔP.E = (24.2 - 10 - 40sin37) x 5

ΔP.E = - 9.87 x 5

ΔP.E = - 49.4 J

Therefore, The net increase in potential energy by the crate is negative 49.4 Joules.

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