Test Your Understanding of Forces and Friction

[cash.money]

Homework Statement

1. The force that propels you forward as you walk across the floor is the force that is exerted by the floor itself. T or F

2. If you were sitting half as far from your nearest classmate, the gravitational force of attraction between the two of you would be four times as strong. T or F

3. For any pair of surfaces, the coefficient of static friction between the surfaces is less than the corresponding coefficient of sliding friction. T or F

Homework Equations

The Attempt at a Solution

 

[musiliu]

1. Hint: This depends on friction or frictionless surface.
2. Hint: Gravity acts downward.
3. Hint: It is harder to get past static friction than kinetic or sliding friction.

 

[nlightner]

1. T: This is true. The force that propels you forward as you walk across the floor is the normal force exerted by the floor, which is equal and opposite to your weight. This force allows you to push off the ground and move forward.

2. F: This is false. The gravitational force of attraction between two objects is dependent on their masses and the distance between them. Halving the distance would only result in a four times increase in force if the masses were also quadrupled.

3. T: This is true. The coefficient of static friction is always greater than the coefficient of sliding friction for any pair of surfaces. This is because it takes more force to overcome the initial static friction and start the motion of an object, compared to maintaining the motion once it has started.