Mechanics (Power): Calculate Horizontal Resistive Force

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Homework Help Overview

The discussion revolves around a mechanics problem related to power and resistive forces acting on a vehicle moving at a constant speed of 55 m s–1, with a given power output of 22 kW from the motors.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the relationship between power, force, and velocity, questioning the application of the formula P=FV. There is uncertainty about identifying the resistive force and the implications of the vehicle moving at a constant speed.

Discussion Status

Participants have acknowledged that the net force acting on the vehicle is zero at constant speed, leading to the conclusion that the driving force equals the resistive force. However, there is no explicit consensus on the calculations or reasoning behind the use of the power formula.

Contextual Notes

Some participants express confusion regarding the formula used and the identification of the resistive force, indicating a need for further clarification on these concepts.

Kajan thana
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Homework Statement



The vehicle now accelerates to a constant speed of 55 m s–1. The useful power output of the motors is 22 kW at this speed.

Calculate the horizontal resistive force acting on the vehicle?
[/B]

Homework Equations


P=FV

The Attempt at a Solution

:

F=P/V[/B]
so the answer is 400N

But what I do not understand is why are we using that formula and how do we know that is the resistive force?
 
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What is the net force acting on the vehicle?
 
cnh1995 said:
What is the net force acting on the vehicle?
I don't know the net force.
 
Kajan thana said:
The vehicle now accelerates to a constant speed of 55 m s–1.
What do you know about the net force from this?
 
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cnh1995 said:
What do you know about the net force from this?
it is zero
 
Kajan thana said:
it is zero
Yes.
So driving force=resistive force.
 
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cnh1995 said:
Yes.
So driving force=resistive force.
Thank you.
 

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