A brick slides on a horizontal surface. Which of the following will increase the frictional force on it?Group of answer choicesIncreasing the speed of the brick as it slidesIncreasing the surface area of contactDecreasing the mass of the brickDecreasing the surface area of contactPutting a second brick on top

The frictional force on the brick can be increased by:

1. Putting a second brick on top: This increases the normal force, which in turn increases the frictional force. The frictional force is directly proportional to the normal force (which is the force exerted by a surface that supports the weight of an object resting on it). So, if you increase the weight of the brick (by putting another brick on top), you increase the normal force and thus the friction.

2. Decreasing the surface area of contact: This might seem counterintuitive, but the frictional force does not depend on the surface area of contact. However, if the surface area is decreased, the weight of the brick is distributed over a smaller area, which could lead to an increase in the pressure between the brick and the surface, and this could increase the frictional force.

The other options (increasing the speed of the brick as it slides, increasing the surface area of contact, and decreasing the mass of the brick) will not increase the frictional force. The frictional force is independent of the area of contact and the speed of the sliding object. And decreasing the mass of the brick would actually decrease the frictional force, because it would decrease the normal force.

The frictional force on the brick can be increased by:

1. Putting a second brick on top: This increases the normal force acting on the brick, which in turn increases the frictional force. The frictional force is directly proportional to the normal force (which is the force exerted by a surface that supports the weight of an object resting on it). So, if you increase the normal force (by adding another brick on top), the frictional force will also increase.

2. Decreasing the surface area of contact: This might seem counterintuitive, but the frictional force does not depend on the surface area of contact. However, if the surface area is decreased, the weight of the brick is distributed over a smaller area, which could lead to an increase in the pressure between the brick and the surface, and thus potentially increase the friction.

The other options (increasing the speed of the brick as it slides, increasing the surface area of contact, and decreasing the mass of the brick) will not increase the frictional force. The frictional force is independent of the area of contact and the speed of the sliding object. And decreasing the mass of the brick would actually decrease the normal force, and thus the frictional force.