Athabasca University PHYS 204 Assignment 3
Assignment 3
The ten questions below cover Units 8-10 and each carries equal weight. You are expected to
solve all questions in detail and submit by uploading to the appropriate drop box. Scanned copy
of your handwritten solutions should be acceptable.
1. A pump draws 750 kg of water per minute from a well 15.0 m deep and ejects it with a speed
of 25.0 m/s, making a vertical fountain.
a. What is the power output of the pump?
b. How high is the fountain? Ignore air resistance.
Work done in lifting the water per minute:
1
W = mgh + mv 2
2
m 1 m 2
W = (750 kg) (9.802
) (15 m) + (750 kg) (25 )
s 2 s
W = 110250 + 234375 = 344625 J
The work done was 3.44 x 105 J.
The power output was:
W 344625 J
P= = = 5743.75 kW
t 60
The power output was 5.74 x 103 J
The water’s height:
kinetic energy (U) = mg⃑h
1
mv 2 = mg⃑h
2
1
(750 kg)(25)2 = (750 kg)(9.80)(h)
2
1
(25)2 = (9.80)(h)
2
312.5 = (9.80)(h)
h = 31.887 m
The fountain is 31.9 m high.
2. The spring shown below has a spring constant equal to 1,500 N/m. It is compressed
18.0 cm, then launches a 400 g block. The horizontal surface is frictionless and the
coefficient of kinetic friction with the incline is 0.15. What horizontal distance d does the
block cover while in the air after it takes off at the top of the incline?
Physics 204: Physics for Scientists and Engineers I 1
Assignment 3
The ten questions below cover Units 8-10 and each carries equal weight. You are expected to
solve all questions in detail and submit by uploading to the appropriate drop box. Scanned copy
of your handwritten solutions should be acceptable.
1. A pump draws 750 kg of water per minute from a well 15.0 m deep and ejects it with a speed
of 25.0 m/s, making a vertical fountain.
a. What is the power output of the pump?
b. How high is the fountain? Ignore air resistance.
Work done in lifting the water per minute:
1
W = mgh + mv 2
2
m 1 m 2
W = (750 kg) (9.802
) (15 m) + (750 kg) (25 )
s 2 s
W = 110250 + 234375 = 344625 J
The work done was 3.44 x 105 J.
The power output was:
W 344625 J
P= = = 5743.75 kW
t 60
The power output was 5.74 x 103 J
The water’s height:
kinetic energy (U) = mg⃑h
1
mv 2 = mg⃑h
2
1
(750 kg)(25)2 = (750 kg)(9.80)(h)
2
1
(25)2 = (9.80)(h)
2
312.5 = (9.80)(h)
h = 31.887 m
The fountain is 31.9 m high.
2. The spring shown below has a spring constant equal to 1,500 N/m. It is compressed
18.0 cm, then launches a 400 g block. The horizontal surface is frictionless and the
coefficient of kinetic friction with the incline is 0.15. What horizontal distance d does the
block cover while in the air after it takes off at the top of the incline?
Physics 204: Physics for Scientists and Engineers I 1
