1. A 1,300 kg car moving at 7 m/s is stopped by the action of its breaks. The wo
ID: 1291952 • Letter: 1
Question
1. A 1,300 kg car moving at 7 m/s is stopped by the action of its breaks. The work done by the car's breaks is ________J.
2. Assume an asteroid is in the shape of a sphere and has a mass of 900 kg. Determine the density (in grams per cubic centimeter) of this asteroid if its diameter is known to be 1 meters.
3. The total energy of an 8.0 kg falling rock is 5,000 J. If its potential energy is 2235 J, the kinetic energy of the rock is _______J.
4. Power is related to
A) how quickly work is done
B) typically measured in kW/hr
C) Both of the answers above
D) None of the above
5. The "law of conservation of energy" is part of a government regulated policy on energy use-- True or False
6. A hunk of cast concrete with a weight of 10N will float if it displaces 11N of water?
Explanation / Answer
1.
work done = 0.5mv^2 =0.5*1300*7^2 = 31850 J
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2.
mass , m = 900 kg
raduis , r = 0.5 m
volume = (4/3)pi*r^3 = 0.5235 m^3
density = mass/volume = 900/0.5235 = 1719 kg/m^3
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3.
totoal energy = potential + kinetic energy
i.e. kinetic energy = 5000-2235 = 2765 J
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4.
A) how quickly work is done
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5.
False
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6.
yes
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