Power Calc: Net vs Driving Force

In summary, when determining power using the equation P=Fv, the force and velocity used must correspond to the type of power being measured. For example, in the case of a cyclist, the power delivered by the foot is calculated using the force applied to the pedal and the tangential velocity of the pedal. The power of the bicycle advancing is calculated using the frictional force and the roadspeed.
  • #1
Janiceleong26
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Homework Statement


P=Fv,
I am confuse with which force to substitute into the equation. Is it the net force? or the driving force? (if it is a car) ..
 
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  • #2
Janiceleong26 said:

Homework Statement


P=Fv,
I am confuse with which force to substitute into the equation. Is it the net force? or the driving force? (if it is a car) ..
It depends on what power is to be determined, but whichever force you pick it must be a velocity that the force travels at.
E.g. a cyclist pushes with a force Fp on a pedal, and the pedal moves at tangential velocity vp. The power delivered by the foot is Pp=Fpvp. The frictional force between the rear tyre and the road is Fr. The bicycle advances at roadspeed vr. The power the tyre/road produces is Pr=Frvr. Because of losses, Pr<Pp.
 
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  • #3
haruspex said:
It depends on what power is to be determined, but whichever force you pick it must be a velocity that the force travels at.
E.g. a cyclist pushes with a force Fp on a pedal, and the pedal moves at tangential velocity vp. The power delivered by the foot is Pp=Fpvp. The frictional force between the rear tyre and the road is Fr. The bicycle advances at roadspeed vr. The power the tyre/road produces is Pr=Frvr. Because of losses, Pr<Pp.

Thanks! I got it now
 

Related to Power Calc: Net vs Driving Force

1. What is the difference between net force and driving force?

The net force is the overall force acting on an object, taking into account all the individual forces acting on it. The driving force, on the other hand, refers to the force that is responsible for initiating or maintaining the motion of an object.

2. How is net force calculated?

Net force is calculated by adding all the individual forces acting on an object. If the forces are acting in the same direction, they are added together. If they are acting in opposite directions, the smaller force is subtracted from the larger force to get the net force.

3. What factors affect the driving force?

The driving force is affected by the mass of the object, the force applied to the object, and any resistance or friction present. The greater the mass, the greater the force needed to overcome it. The greater the force applied, the greater the driving force. Resistance or friction can decrease the driving force.

4. How does net force affect an object's motion?

According to Newton's Second Law of Motion, the net force acting on an object is directly proportional to its acceleration. This means that the larger the net force, the greater the acceleration of the object. If the net force is zero, the object will either remain at rest or continue moving at a constant velocity.

5. What is the relationship between net force and driving force?

The driving force is a type of net force, as it is the overall force responsible for the motion of an object. However, there may be other forces acting on the object in addition to the driving force, resulting in a net force that is different from the driving force. In other words, the driving force is just one component of the net force acting on an object.

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