Question

A car cruises down the highway at constant velocity 50 mph. The backwards force of wind resistance and friction have a combined strength of 5000 newtons. The car’s engine causes a forward force to be exerted on the car. Is this forward force less than 5000 newtons, equal to 5000 newtons, or greater than 5000 newtons?

Answer 1

It is equal to 5000 Newtons

Step-by-step explanation:

According to the second Newton law, the net force that acts over a body is equal to its mass multiplied by its acceleration. In this case, we know that there is a force of 5000 N which is contrary to the movement, and which is overcome by a force that the engine causes. We also know that there is no acceleration, because the velocity is a constant (the acceleration is the change of velocity through the time).

The net force
`F_N` over the car is:

`F_N=F_(engine)-F_(RyF)`

Where N subscript means net, and RyF subscript means the resistance and friction; for the second law we have:

`F_N=m*a`

But,
`a=0`, so:
`F_(N)=0`

`F_(engine)=F_(RyF)=5000N`

Always you have a body without acceleration (or constant velocity, even zero), the net force acting on it is zero because the Newton second law says us that if there were a force, there would be acceleration.