Newton’s first law of motion states that an object remains at rest unless a ____ force act on it

Question

A.balenced 

B.Frictional 

C.gravitational

D.unbalenced

Answer 1

Unbalanced. In many textbooks you'll also find the term "net force" used instead of unbalanced but the meaning is the same. According to Newton's 1st Law of Motion, an object's motion will not change unless there is a force that is not cancelled out by another force acting on it thus that force must by definition be unbalanced. 

 

Choice B: frictional doesn't make much sense because we know that static friction acts on objects at rest by definition. 

 

Choice C: gravitational isn't correct because we know you can move an object (for example by throwing it) even in the absence of gravity

 

Choice A: balanced force is incorrect because according to Newton's second law F_net=ma, a balanced force causes no acceleration therefore no change in motion.