MOMENTUM & IMPULSE
Momentum
The product of an object’s mass and its velocity
p=mv
Measured in kgms-1
Vector (direction same as direction of velocity)
Directly proportional to velocity
Change in momentum
p = mv
Change in momentum is in the same direction as the force causing
the change
If the Fnet acting on the object = 0, there is no change in
momentum
Newton’s 2nd Law of Motion in terms of Momentum
The resultant force acting on an object is equal to the rate of
change of momentum of the object in the direction of the resultant
force
Fnet = p∆t
Conservation of Momentum
The total linear momentum of a closed system remains constant
Isolated system a system free from the influence of a net external
force (law only applies to isolated systems)
Total momentum before collision = total momentum after collision
mAvAi+mBvBi= mAvAf+mBvBf where f = after the collision and i = before
the collision
Must choose a + direction when applying law
Collisions
There are 3 types of collisions:
1. Start with 2 objects and end with 2
2. Start with 1 object and end with 2 (explosion)
3. Start with 2 objects and end with 1
Momentum is always conserved in collisions
Kinetic Energy isn’t always conserved- objects deform (give off
light, produce sound, heat up, change shape)
Momentum
The product of an object’s mass and its velocity
p=mv
Measured in kgms-1
Vector (direction same as direction of velocity)
Directly proportional to velocity
Change in momentum
p = mv
Change in momentum is in the same direction as the force causing
the change
If the Fnet acting on the object = 0, there is no change in
momentum
Newton’s 2nd Law of Motion in terms of Momentum
The resultant force acting on an object is equal to the rate of
change of momentum of the object in the direction of the resultant
force
Fnet = p∆t
Conservation of Momentum
The total linear momentum of a closed system remains constant
Isolated system a system free from the influence of a net external
force (law only applies to isolated systems)
Total momentum before collision = total momentum after collision
mAvAi+mBvBi= mAvAf+mBvBf where f = after the collision and i = before
the collision
Must choose a + direction when applying law
Collisions
There are 3 types of collisions:
1. Start with 2 objects and end with 2
2. Start with 1 object and end with 2 (explosion)
3. Start with 2 objects and end with 1
Momentum is always conserved in collisions
Kinetic Energy isn’t always conserved- objects deform (give off
light, produce sound, heat up, change shape)
