# How much work is done by the horizontal force?

http://session.masteringphysics.com/problemAsset/1...

A) How much work is done by the horizontal force Fp = 150 N on the 18-kg block of the figure when the force pushes the block 4.0m up along the 32 degree frictionless incline?

B) How much work is done by the gravitational force on the block during this displacement?

C) How much work is done by the normal force?

D) What is the speed of the block (assume that it is zero initially) after this d is placement? [Hint: Work-energy involves net work done.]

Any help you can give is appreciated. Even detailed hints, formulas, and explaination to get me started would be awesome! Thanks.

• http://hyperphysics.phy-astr.gsu.edu/hbase/imgmec/...

A)

W = Fp cos 32 * 4 = 150 * 0.848 * 4 = 508.8 J

B)

W = m g sin 32 = 18 * 9.8 * 0.53 * 4 = 373.97 J

C)

Normal force = m g cos 32 + F sin 32 = 18* 9.8 * 0.848 + 150* 0.53 = 229.08 N

This force is perpendicular in the travel and its work W = 0 in the abscence of friction

C1)

F net = F cos 32 - m g sin 32 = 150 * 0.848 - 18 * 9.8 * 0.53 = 127.2 - 93.49 = 33.71N

W = 33.71 * 4 = 134.84 J

D)

Acceleration -- a = Fnet / m = 33.71 / 18 = 1.872 m/s2

Velocity block after 4m

e = 1/2 a t^2 --- t^2 = 2e / a = 8 / 1.872 = 4.27 --- t = √4.27 = 2.0668 s

velocity = a * t = 1.872 * 2.0668 = 3.869 m/s

http://hyperphysics.phy-astr.gsu.edu/hbase/faia.ht...

Goodbye

• for part B answer is Negative make sure that

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