Question

Are the statements below correct? With the presence of kinetic friction, an object pulled by gravity can no longer slide down an inclined plane at a constant acceleration. Considering two ways in the right figure to push two identical heavy boxes to move, no one is less strenuous than the other for overcoming the kinetic friction. When a car is speeding up, the friction force on the tire from the road has a different direction from that when the car is slowing down. When a rotating wheel is suddenly placed on the road, the kinetic friction will deaccelerate the rotation but accelerate a translational motion of the wheel.

Answer 1

5)

1. Sliding of an object down an inclined plane at a constant acceleration depends on the force acting downward the object in that inclined plane. If this downward force is more than the friction force, the object will slide, otherwise not. More is the value of coefficient of kinetic friction, lesser will be the downward force.

2. In the figure a, the two boxes will have a common acceleration upon the application of a force. They will move together as single system. There will be no kinetic friction in this system.

In the figure b, if the maximum force that can be applied on the system is greater than any other force value, both boxes will move together with a common acceleration. The upper box will not slide over the lower box. Otherwise, the upper box will begin to slide over the lower box and both will have different acceleration values.

The applied maximum force will directly depend on the coefficient of kinetoc friction.

3. The friction force always acts in a direction opposite to that of motion. While accelerating, the driving force overcomes the friction force. While slowing down, the driving force is reduced and friction force and any other resistive force continue to increase.

4. For a rotating wheel, there will be static friction only. There will be no kinetic friction. There will be no energy dissipation due to static friction on the wheel. The resistance of a static friction causes rolling motion and prevents a body from sliding forward. The wheel will have translational motion only if static friction ceases to exist.