Answer:
Gravitational
Tension
Normal
Friction.
Explanation:
The forces acting on the sled are:
Tension: the tension from the rope, this is the force that "moves" the sled.
Friction: kinetic friction between the sled and the ground as the sled moves.
There are another two forces that also act on the sled, but that "has no effect"
Gravitational force: This force pulls the sled down, against the floor.
Normal force: This force "opposes" to the gravitational one, so they cancel each other.
These two forces cancel each other, so they have no direct impact on the movement of the sled. BUT, the friction force depends on the weight of the moving object, and the weight of the moving object depends on the gravitational force, so we need gravitational force in order to have friction force.
Then we can conclude that the forces acting on the sled are:
Gravitational
Tension
Normal
Friction.
We can find the average speed of the body by finding the total distance covered, and then dividing it by the total time of the motion.
The total distance covered is:

while the total time of the motion is

So, the average speed of the body is:
A boiling pot of water (the water travels in a current throughout the pot), a hot air balloon (hot air rises, making the balloon rise) , and cup of a steaming, hot liquid (hot air rises, creating steam) are all situations where convection occurs.
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