Kamala puts on inline skates and stands facing a wall. When she pushes against the wall, she rolls backward. Why does pushing ha
2 answers:
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Answer:
87.1 mph
Explanation:
We are given that
Mass,m=60 kg
Power,P=340 W
Speed,v=5 m/s
Area,
Drag coefficient,
Coefficient of rolling resistance,
Friction force,
Where
Let speed of cyclist=v'
Drag force,
Density of air,
Power,P=
1 m=0.00062137 miles
1 hour=3600 s
To solve this problem we will apply the first law of thermodynamics and we will make a balance between the heat transferred, its internal energy and the total work. Recall that for gases the definition of work can be expressed in terms of its pressure and volume. Let's start
Here,
dU = Internal Energy
dW = Work
But internal energy is unchanged, then
Where
= Change in Volume
P = Pressure
Finally, the expression of the heat transferred can be expressed in terms of pressure and volume, so it would end up becoming
Replacing,
Therefore the correct answer is B.
To solve this problem we will apply the concept of rotational kinetic energy. Once this energy is found we will proceed to find the time from the definition of the power, which indicates the change of energy over time. Let's start with the kinetic energy of the rotating flywheel is
Here
I = moment of inertia
Angular velocity
Here we have that,
Replacing the value of the moment of inertia for this object we have,
The expression for average power is
Therefore the correct answer is 620s.