This paper examined five physics problems. The physics problems covered work, energy, and momentum. They also examined the height of a ball thrown into the air at a certain initial velocity. They also required conversion between English and metric measurement systems. The problems are stated, all work for the problems is shown, and the answers are in bold.
Work, Energy, And Momentum
Work out the following problems. Be sure to show your work in detail. See the " uploaded file for examples of how the problems should be solved.
A freight elevator has a mass of 3,000 kg, including cargo. The elevator motor raises the load 50 m in 30 s. How much work is done by the motor? What is its power?
W= F*d
F=m*a
W=m*a*d
W= 3000kg *9.8m/s2*50m
W= 1,470,000J
P=W/t
P=1,470,000J/30s
P= 49,000W
What is the KE (in J) of a 2650 lb Honda Civic traveling at 100 mph?
KE=1/2mv2
Conversions from English to metric m=2650lb * 1kg/2.2 lb m=1204.55kg
100 mph * 1 hr/3600 sec * 1609.344 m/mi= 44.7 m/s
KE= 1/2 * 1204.55kg * (44.7m/s2)
KE= 1,203,399.7 J
A standard baseball weights 145 g. If it is thrown vertically with an initial velocity of 50 mph, what is its potential energy change at its highest point? How high does the baseball rise? Neglect air friction.
h=v2/2g
conversion from English to metric
mph *.44704 m/s
1 mph
22.352m/s h= (22.352 m/s) 2/2*9.8m/s2
h=25.49m
PE=Fd; F=ma
PE=m*a* d
PE=145g* 9.8m/s2* 25.49m
PE= 36,221.29J
4. Previously, we calculated the KE of a 2650 lb Honda Civic traveling at 100 mph. What is its momentum?
P=mv
P=2650lb * 1kg/2.2.lb * 100m/h * .44704m/s / 1 mph
P=20.32 kgm/s
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