3. how difficult it is to change an object's motion
Answer:
F = 0
Explanation:
Newton's second law is
F = ma
As in this case the two blocks move with constant speed, it implies that the acceleration is zero, therefore the force applied to the system is zero
F = 0
Answer:
The external stimulus of fear.
Explanation:
The zebras would most likely be scared of the lions, due to the fact that the lions want to eat the zebra. Thus leading to the zebra's running away from the lions.