Work And Power Practice 2 Answers 27316q

WORK AND POWER #2 Solve the following problems. Show all your work. to include the correct units. COMPLETE THIS ON A SEPARATE SHEET OF PAPER! 1. How much work is done by a crane that lowers 1000 newtons of material a distance of 150 meters? W=Fxd W=?J F = 1000 N d = 150 m W = 1000 N x 150 m W = 150,000 J 2. How much work is done when a 1-kilogram mass is raised a vertical distance of 1 meter? w = mg w = 1 kg x 9.8 m/s2 W=Fxd F = 9.8 N d=1m W = 9.8 N x 1 m W = 9.8 J 3. A 5-kilogram rock is lifted 2 meters in 5 seconds. a. How much work is done? w = mg w = 5 kg x 9.8 m/s2 w = 49 N W=Fxd W=?J F = 49 N d=2m W = 49 N x 2 m W = 98 J b. What power is used? P=

𝒘𝒐𝒓𝒌 𝒕𝒊𝒎𝒆

P=?W W = 98 J t=5s

P=

𝟗𝟖 𝑵 𝟓𝒔

P = 19.6 W 4. A teacher pushed a desk across a floor for a distance of 5 meters. She exerted a horizontal force of 20 newtons. How much work was done? W=Fxd W=?J F = 20 N d=5m W = 20 N x 5 m W = 100 J 5. A weight lifter lifts a 150-kg barbell above his head from the floor to a height of 2m. He holds the barbell there for 5 sec. How much work does he do during that 5-sec interval? During the 5 second interval there is no movement from the weight lifter. If there is no movement there is no work being done. 6. A student who weighs 500 newtons climbed the stairs form the first floor to the third floor, 15 meters above, in 20 seconds. a. How much work did she do? W=Fxd W=?J F = 500 N d = 15 m W = 500 N x 15 m W = 7,500 J b. What is her power? P=

𝒘𝒐𝒓𝒌 𝒕𝒊𝒎𝒆

P=?W W = 7,500 J t = 20 s P=

𝟕,𝟓𝟎𝟎 𝑱 𝟐𝟎 𝒔

P = 375 W 7. A box is pushed across the floor for a distance of 5 meters with a force of 50 newtons in 5 seconds. a. How much work is done?

W=Fxd W=?J F = 50 N d=5m W = 50 N x 5 m W = 250 J b. What is her power? P=

𝒘𝒐𝒓𝒌 𝒕𝒊𝒎𝒆

W = 250 J t=5s P=

𝟐𝟓𝟎 𝑱 𝟓𝒔

P = 50 W 8. A woman lifts a 35-kg child a distance of 1.5 meters and carries her forward for 6.5 m. a. How much work does the woman do in lifting the child? w = mg w = 35 kg x 9.8 m/s2 w = 343 N W=Fxd F = 343 N d = 1.5 m W = 343 N x 1.5 m W = 514.5 J b. How much work does the child do? The child does not do any work. The child is pushing down with a 343 N force while moving upward. The force and the distance are not acting in the same direction. 9. If 4000 Joules are used to raise a 30-kilgrams mass, how high is the mass raised? w = mg w = 30 kg x 9.8 m/s2 w = 294 N W=Fxd W = 4,000 J F = 294 N d=?m 4,000 J = 294 N x d d = 13.6 m 10. A force used to lift a 12-kilogram mass to a height of 8 meters in 2 seconds does 1040 joules of work.

a. How much force is used? W = 1040 J F=? N d=8m 1040 J = F x 8 m F = 130 N b. What power is developed? P=

𝑾𝒐𝒓𝒌 𝒕𝒊𝒎𝒆

W = 1040 J t=2s P=

𝟏𝟎𝟒𝟎 𝑱 𝟐𝒔

P = 520 W