A force of 1000 newtons was necessary to lift a rock. A total of 3000 joules of work was done. How far was the rock lifted?
1 answer:
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A) The change in internal chemical energy is
B) The time needed is 1 minute
Explanation:
First of all, we start by calculating the power output of you and the bike, given by:
where
F = 80 N is the force that must be applied in order to overcome friction and travel at constant speed
v = 8.0 m/s is the velocity
Substituting,
The energy output is related to the power by the equation
where:
P = 640 W is the power output
E is the energy output
is the time elapsed
Solving for E,
Since the body is 10% efficient at converting chemical energy into mechanical work (which is the output energy), this means that the change in internal chemical energy is given by
B)
From the previous part, we found that in a time of
t = 30 min
the amount of internal chemical energy converted is
Here we want to find the time t' needed to convert an amount of chemical energy of
So we can setup the following proportion:
And solving for t',
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