Conservation of Energy, Car Driving with Drag Force

AI Thread Summary
To determine the power required for a 710kg car driving at a constant speed of 23m/s against a drag force of 500 N, the power consumption can be calculated using the formula: Power (Watts) = Force (N) * Speed (m/s). On level ground, the mass of the car is irrelevant since it moves at constant speed, and only the drag force needs to be considered. For driving uphill at a 2.0° slope, the gravitational force component must be added to the drag force to find the total opposing force. The discussion highlights the importance of understanding forces and power calculations in physics, particularly in scenarios involving constant speed and drag.
David Mordigal
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Homework Statement


A 710kg car drives at a constant speed of 23m/s . It is subject to a drag force of 500 N. What power is required from the car's engine to drive the car (a) on level ground? (b) up a hill with a slope of 2.0o? Express your answer to two significant figures.

Homework Equations


p = mv
P = ΔW/Δt (but no time information given)

The Attempt at a Solution


I am not sure where to begin. I understand that power is the change in work with respect to time, but there is no time information given in the problem, so I am a little lost.
 
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The car is moving on level ground and up the hill at constant speed. Speed has got time in it. Why can't you use that?
 
Since constant speed is the situation, the for and against forces are equal.
On level ground the mass of the car doesn't come into it.
Then :
Power consumption ( Watts ) = force overcome (N) * speed (m/s)
(applies to constant or instantaneous speed only)
In the uphill problem, calculate the additional force acting against the car and down the slope due to gravity ( m * g * sine (2 ° ) ) and add to the 500 Newtons of drag, then calculate the power consumption.
 
This question is probably moot by now, given that it was first posted in Nov. 2014 and the OP never replied.
 
OK, thanks
 

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