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

• KatieLynn
In summary, when an automobile moves at a constant velocity, the power developed is used to overcome frictional forces from the air and road. If the engine develops 30 horsepower, the total frictional force acting on the car at 120 mph is approximately 53.6448 m/s. To calculate the force, the power and velocity can be multiplied together without converting units.
KatieLynn

## 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?

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.

## 1. What is work and friction?

Work and friction are both physical concepts related to the movement of objects. Work is the measure of energy transfer that occurs when a force is applied to an object and it moves in the direction of the force. Friction is the force that opposes the relative motion of two surfaces in contact with each other.

## 2. How is work calculated in a friction problem?

To calculate work in a friction problem, you need to know the magnitude of the force applied to an object and the displacement of the object in the direction of the force. The work done is equal to the product of these two values.

## 3. What factors affect the amount of friction in a problem?

The amount of friction in a problem is affected by several factors, including the type of surfaces in contact, the force pushing the surfaces together, and the roughness of the surfaces. Additionally, the presence of lubricants or other substances between the surfaces can also affect the amount of friction.

## 4. How does friction impact the efficiency of a machine?

Friction can reduce the efficiency of a machine by converting some of the input energy into heat. This means that less of the initial energy is available to do useful work. Reducing friction through the use of lubricants or smoother surfaces can help improve the efficiency of a machine.

## 5. Can friction ever be a beneficial force?

Yes, friction can be a beneficial force in certain situations. For example, friction is necessary for walking, as it provides the necessary traction between our shoes and the ground. Friction can also be useful in slowing down objects, such as using brakes to stop a car or using friction to control the speed of a roller coaster.

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