Let's say I put the brakes on really suddenly in a car that was moving at 40mph. If I know how much force it takes to break the adhesion of the wheels, how do I find the force the car is exerting? Since I'm not giving it any gas, I won't be accelerating, but it has to be exerting force or I wouldn't be skidding.
In short, how do I find the force of an object that's coasting? I assume it has something to do with momentum, but I'm a newbie so I'm a little lost.
Edit: sorry, this was worded badly. I meant how do I find the force that the object will exert on you if you try to stop it. I knew the engine in the car isn't producing force, I just don't understand what force is causing the car not to adhere to the road. I guess what I'm trying to ask is "where is the force coming from that causes a coasting car to skid?" It makes sense that the car is only slowing down because of the brakes, but what causes the tires to lose adhesion if you apply the brakes too fast and lock up the wheels?
Best Answer
Just because an object is in motion, that doesn't mean that there is a force acting on it. Newton's 1st law states that an object in motion will stay in motion unless acted on by an outside force. So the car's momentum is what keep's it going as it coasts. The forces acting on the car would be gravity, the normal force (the ground pushing up on it), and friction slowing it down, but no force is pushing it forward. The skidding is coming from the friction of the wheels touching the road.To sum things up, no force is being applied to the car by you.