Newton's second law states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. If the net force on an object is zero, its velocity will be constant. The direction of the acceleration is always the same as the direction of the net force.

1. PHYSICS
NEWTON’S SECOND LAW.

2. NEWTON’S SECOND LAW
Acceleration
(m/s2)
According to the second law, a net force on an object causes it to
accelerate. If an object accelerates, its velocity must change.
Net force (N)
Mass (kg)
Velocity must change if a net force acts on an object.

3. NEWTON’S SECOND LAW
The acceleration of an object is directly proportional to the
net force acting on it and inversely proportional to its mass
m
F
m
F
a net






a
m
F
Fnet




 

4. UNITS OF FORCE
2
s
m
kg
1
N
1 
SI unit of force is a Newton (N)

5. CONSTANT VELOCITY
Acceleration
(m/s2)
If velocity stays constant, then the acceleration is
zero—so the net force must also be zero.
Net force (N)
Mass (kg)
The net force is zero on an object with constant velocity.

6. DIRECTION OF FORCE AND ACCELERATION
Acceleration and force are
vectors.
The acceleration is always in the
direction of the net force.

7. EXPERIMENT

8. 1 - QUIZ
A student drags a 10 kg box
across a rough level floor with a
constant velocity of 1.5 m/s.
What is the net force on the box?

9. 2 - QUIZ
A student drags a 10 kg box
across a rough level floor with a
constant acceleration of 1.5 m/s.
Now what is the net force on the
box?

10. 3 - QUIZ
The force F1 acts on a puck that moves over frictionless ice along
an x axis, in one-dimensional motion. The puck's mass is m = 0.20
kg. Force F1 isdirected along the x axis and have magnitudes F1 =
4.0 N. Find the acceleration of motion

11. 4 - QUIZ
Two forces act on a puck that moves over frictionless ice along
an x axis, in one-dimensional motion. The puck's mass is m =
0.20 kg. Forces F1 and F2 and are directed along the x axis and
have magnitudes F1 = 4.0 N and F2 = 2.0 N.
Find the acceleration of motion

12. 5 - QUIZ
Two forces act on a puck that moves over frictionless ice along an x
axis, in one-dimensional motion. The puck's mass is m = 0.20 kg.
Forces F1 and F3 respectively, and have magnitudes F1 = 4.0 N and
F3 = 1.0 N. F3 is directed at angle q = 30°. FInd the acceleration of
the puck?

13. 6 - QUIZ
The cup of ayran having mass 0.60-kg slides from the end of the
counter to a thirsty customer. A force of friction of 1.2 N brings
the drink to a stop right in front of the customer.
a) What is the acceleration of root beer?
b) What is the coefficient of kinetic friction between the glass
and the counter?
0.60 kg
Ffr
Fn
mg = 6N

14. THANK YOU!