Newton's Laws of motion

Newton’s first law

• when no net force acts on an object then

  • if the object is at rest, it will remain at rest

  • if the object is moving, it will continue to move in a straight line at a constant speed

• no net force→no acceleration

if no net force and object is at rest then it will continue to be at rest, if no net force and object is moving then it will continue to move at a constant speed. 

summarize newton’s first law

no net force→no acceleration

remember: no net force→no acceleration

the weight and the normal force have equal mags and opp directions so they cancel out

remember: the weight and the normal force have equal mags and opp directions so they cancel out 

Newton’s second law 

• the net force acting on an object is equal to its mass times its acceleration

  • F→net = m×a→

  • fnet = ma

apply Newtons second law (fnet = ma) to each component separately (to x component and then to y component, NOT all together)

remember: apply Newtons second law (fnet = ma) to each component separately (to x component of accel and then to y component of accel, NOT all together)

problem-solving strategy

1) draw free-body diagram

2) break up the forces into their components

3) apply newton’s second law:

• fnet = 0 for objects not accelerating

• fnet = ma for object that are accelerating

1) draw free-body diagram 2) break up forces into their components 3) apply newtons second law

summarize the problem-solving strategy

Fnet = 0

if the object is not accelerating the net force is what?

Fnet = ma

if the object is accelerating the net force is what?