Adogsled is moving at a constant speed of 3.0 m/s in a straight line on level ground,
and each dog is exerting a force of 15 n along that same straight line. what is the
magnitude of the net force on the sled and its occupants during this movement?
80 n
60 n
more than 80 n
0 n

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).

moving ball hits still ball. mover stops, hit ball moves. momentum transfer.