On a calm day with no wind, you can run a 1500-m race at a velocity of 4.0 m/s. If you run the same race on a day when you have
2 answers:
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We can solve the problem by using the first law of thermodynamics:
where
is the change in internal energy of the system
is the heat absorbed by the system
is the work done by the system on the surrounding
In this problem, the work done by the system is
with a negative sign because the work is done by the surrounding on the system, while the heat absorbed is
with a negative sign as well because it is released by the system.
Therefore, by using the initial equation, we find
Answer:
c.
Explanation:
- In absence of friction, total mechanical energy must be conserved.
- This means that the change in gravitational potential energy (in magnitude) must be equal to the change in kinetic energy:
- As it can be seen, the mass m is on the both sides of the equation, which means that it can be simplified.
- We can solve this equation for v (speed at the bottom) as follows:
- As it can be seen, the mass has no part in the equation, so, due both are starting from the same height, both people have the same speed at the bottom.
- The option c is the right one.