1. Static friction: When a car is at rest, the force required to overcome static friction is greater than the force required to keep it moving once it is in motion. This is because the molecules of the car's tires and the road surface have time to interlock, creating a stronger bond that is more difficult to overcome.
2. Inertia: Inertia is the tendency of an object to resist changes in its state of motion. When a car is at rest, it has zero momentum. To get it moving, you have to overcome its inertia and accelerate it from zero velocity to some positive velocity. This requires a greater force than simply keeping it moving once it is already in motion.
3. Rolling resistance: When a car is rolling, the tires also experience rolling resistance, which is the force that resists the rotation of the tires on the road surface. This force is proportional to the weight of the car and the coefficient of rolling resistance between the tires and the road. Rolling resistance contributes to the overall force required to push the car from rest.
4. Weight of the car: The weight of the car is another factor that makes it more difficult to push from rest. The heavier the car, the greater the force that is required to overcome inertia and rolling resistance and get it moving.
In summary, the combination of static friction, inertia, rolling resistance, and the weight of the car makes it more difficult to push a car from rest compared to keeping it moving.
