How large is the average friction force?

How do I find force of friction?

• What force is required to accelerate a 1500 kg car at an acceleration of 3.00 m/s^2? If you need to apply 5500N to achieve this acceleration, what is the force of friction that opposes the movement of the car? Is there a specific equation of finding friction or opposite forces? I only understand the netforce = mass times acceleration. I do not understand the equation for Newtons 3rd law of F1 on 2 = -F2 on 1 Please explain

• Answer:

  Force = mass* acceleration = 1500*3 = 4500N. But we need 5500N to achieve this. It means a force of (5500 -4500) = 1000N is opposite to our applied force, which is the frictional force = -1000 N, Minus to indicate that it is opposite to the 5500 N. ============================= Consider two balls 1 and 2 are moving toward each other. Ball 1 is moving from left to right and ball 2 is moving from right to left. Suppose that after collision both the balls stop. Ball 1 is stopped because the ball 2 exerted a force on ball 1. Similarly ball 2 is stopped because the ball 1 has exerted a force on 2. Newton’s law states these two forces will be equal but opposite. It is important to note that the two forces act on different objects and not on one and the same object. F2 acts on ball 1. F1 acts on ball 2. Hence they cannot cancel each other. ======================================