Answer:
0 N
Explanation:
The key for solving the problem is in the sentence "moving at a constant speed in a straight line".
In fact, this means that the velocity of the sled is constant: and therefore, that its acceleration.
Newton's second law states that:
F = ma
where
F is the net force on an object
m is its mass
a is its acceleration
In this problem, we have asserted that the acceleration of the sled is zero:
a = 0
Therefore, according to the equation above, this also means that the net force on the sled is also zero:
F = 0 N
(This implies that there must be another force, must like the force of friction, that acts backward, in the opposite direction to the pull applied by the dogs).
