What is the frictional force acting on a car at 120 mph with a 30 hp engine?

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To find the frictional force acting on a car with a 30 hp engine traveling at 120 mph, first convert horsepower to watts, resulting in 22,380 watts. The speed of the car is approximately 53.645 m/s. Using the power formula, power equals force times velocity, the frictional force can be calculated by rearranging the equation to force equals power divided by velocity. Therefore, the frictional force is determined by dividing 22,380 watts by 53.645 m/s, yielding the total frictional force in Newtons. The discussion emphasizes the importance of correctly applying the power and velocity relationship to solve for force.
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Homework Statement


When an automobile moves with constant velocity, the power developed is used to overcome the frictional forces exerted by the air and the road. If the engine develops 30 hp, what total frictional force acts on the car at 120 mph?


Homework Equations


1hp = 746W
1mile-1609m
work=force*distance
power= work/time

The Attempt at a Solution



30hp= 22380w
120mph= 53.6448m/s
I'm really not sure where to go from there, you need to end up with force which is Newtons, don't you need a mass in kg to for that?
 
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Power = Force*velocity.
 
so can you just multiply 22380w and 53.6448m/s, or do you have to change the watts to another unit?
 
oopps you have to divide them actually right?
 
Yes. No need to change anything.
 

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