Download I.E. BLOCK on a ROUGH SURFACE

January 05, 2015
I.E. BLOCK on a ROUGH SURFACE
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January 05, 2015
1. A 50 kg block is pulled from rest by a force of 100 N at 37° across a horizontal rough surface over a distance of 5.6 m. The coefficient of kinetic friction between the block and the surface is 0.5.
a. Draw a free­body diagram and show all the applied forces.
b. How much work is done by force F?
c. How much work is done by the normal force?
d. How much work is done by the gravitational force?
e. How much work is done by the friction force?
f.
What is the net work done on the block?
g. What is the change in kinetic energy of the block?
h. What is the final velocity at 5.6 m?
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January 05, 2015
1. A 50 kg block is pulled from rest by a force of 100 N at 37° across a horizontal rough surface over a distance of 5.6 m. The coefficient of kinetic friction between the block and the surface is 0.5.
a. Draw a free­body diagram and show all the applied forces.
FN
F
Ff
mg
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January 05, 2015
1. A 50 kg block is pulled from rest by a force of 100 N at 37° across a horizontal rough surface over a distance of 5.6 m. The coefficient of kinetic friction between the block and the surface is 0.5.
b. How much work is done by the applied force F?
W = FΔx(Cos θ)
W = (100 N)(Cos37)(5.6 m)
W = 4472 J
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January 05, 2015
1. A 50 kg block is pulled from rest by a force of 100 N at 37° across a horizontal rough surface over a distance of 5.6 m. The coefficient of kinetic friction between the block and the surface is 0.5.
c. How much work is done by the normal force?
0 J
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January 05, 2015
1. A 50 kg block is pulled from rest by a force of 100 N at 37° across a horizontal rough surface over a distance of 5.6 m. The coefficient of kinetic friction between the block and the surface is 0.5.
d. How much work is done by the gravitational force?
0 J
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January 05, 2015
1. A 50 kg block is pulled from rest by a force of 100 N at 37° across a horizontal rough surface over a distance of 5.6 m. The coefficient of kinetic friction between the block and the surface is 0.5.
e. How much work is done by the friction force?
1. ΣF = ma
2. FN + FSinθ = mg Solving for FN FN = mg ­ FSinθ 3. Ff = μFN = μ(mg ­ FSinθ) = (.5)[(50)(9.8) ­ 100 Sin37°] = 214.8 N
4. W = FfΔx W = (214.8 N)(5.6 m) = 1203 J
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January 05, 2015
1. A 50 kg block is pulled from rest by a force of 100 N at 37° across a horizontal rough surface over a distance of 5.6 m. The coefficient of kinetic friction between the block and the surface is 0.5.
f. What is the net work done on the block?
W = FnetΔx
W = (100N Cos37 ­ 214.8 N)(5.6 m)
W = (798.63 ­ 214.8)5.6 = 3269.47J
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January 05, 2015
1. A 50 kg block is pulled from rest by a force of 100 N at 37° across a horizontal rough surface over a distance of 5.6 m. The coefficient of kinetic friction between the block and the surface is 0.5.
g. What is the change in kinetic energy of the block?
ΔKE = Wapp ­ Wf
ΔKE = 4,472J ­ 1,203J = 3,269J
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January 05, 2015
h. What is the final velocity?
Wnet = ∆ KE
3,269J = .5 (50) v2
V = 11.43 m/s
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January 05, 2015
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