If only an external force can change the velocity of a body, how can the internal force of the brakes bring a car to rest? 1. It is the driver, not the car itself who causes the breaking, so it is an external force. 2. The engine is stopped, so the car has no force to run further. 3. Some internal forces can change the velocity of a body. 4. It is the force of the road on the tires (an external force) that stops the car.

Answer :

lcmendozaf

Answer:

4. It is the force of the road on the tires (an external force) that stops the car.

Explanation:

If there is no friction between the road and the tires, the car won't stop.

You can see this, for example, when there is ice on the road. You can still apply the brakes (internal force), but since there is no friction (external force) the car won't stop.

The force of the brakes on the wheels is not what makes the car stop, it is the friction of the road against still tires that makes it stop.

Friction force is the product of normal force and coefficient of friction. It is the force of the road on the tires (an external force) that stops the car.

What is friction force?

The force that is exerted by a surface on the object as it moves across it or makes an effort to move across it is known as the frictional force.

As we know the car is moving on the road therefore, has applied to be friction force between the car and the road. Now when the brake is applied the movement of the car tire will stop, therefore, the friction force between the car tire and the road will increase.

Hence, It is the force of the road on the tires (an external force) that stops the car.

Learn more about Friction Force:

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