because of friction, a constant force of 20 N is needed to slide a box across a room to the right at a constant speed, and box is moved 3 m.

What is the friction force and how much work is done by friction force??

How much work is done by gravity?
How much work is done by normal force(upward)?

So, if v(speed) is constant, then acceleration=0 and net force=0????

Yes to your last question. Since it does not accelerate, the friction force equals the applied force, 20 N.

Since one can assume the floor of the room is level, gravity does no work. It acts perpendicular to the direction of motion. The same applies to the upward force.

The friction force does negative work (absorbs energy) equal to work done by the applied force, 20 x 3 = 60 J

So to summarize:

- The friction force is equal to the applied force, which is 20 N.
- The work done by friction force is negative, equal to -60 J (20 N x 3 m).
- The work done by gravity and normal force is both 0 J, as both forces act perpendicular to the direction of motion.
- And yes, since the speed (v) is constant, the acceleration is 0, and the net force is also 0.

The friction force is 20 N, and the work done by the friction force is 60 J.

The work done by gravity is 0 J since it acts perpendicular to the direction of motion.

The work done by the normal force (upward) is also 0 J since it also acts perpendicular to the direction of motion.

To calculate the friction force, you need to understand that when an object is moving at a constant speed, the net force acting on it is zero. In this case, the constant force of 20 N is needed to overcome the friction force and maintain the box's motion. Therefore, the friction force is equal to the applied force, which is 20 N.

To determine the work done by the friction force, you can use the equation: Work = Force x Distance. In this case, the force of friction is 20 N, and the distance the box is moved is 3 m. Therefore, the work done by the friction force is calculated as follows: Work = 20 N x 3 m = 60 J (Joules). The negative sign indicates that the work done by the friction force is in the opposite direction of motion.

Since the box is not being lifted or lowered, the force of gravity does not do any work. Gravity acts vertically downward, perpendicular to the direction in which the box is being moved. Therefore, gravity does not contribute to the work done in this scenario.

Similarly, the normal force, which is the force exerted by the surface on the box in the upward direction, does not do any work. It acts perpendicularly to the direction of motion, so no work is done by the normal force.

To summarize, the friction force is 20 N, the work done by the friction force is 60 J (negative value), the work done by gravity is 0 J, and the work done by the normal force is 0 J.