1.5 form 4 e_momentum
TRANSCRIPT
1. MOMENTUMAn object with mass moving at a certain speed has momentum.
When a moving vehicle runs into a stationary one, the stationary vehicle is pushed forth to some point. This means that momentum is transferred from the moving vehicle to the stationary one.
Momentum is defined as: The product of mass and velocity.
p = m.v
Momentum is measured in kg.m/s.
Momentum is a vector quantity. It has magnitude and direction.
Example + exercise
Exercise
Determine the momentum of:
1. A 60kg woman moving eastward at
9m/s.
2. A 10 tone truck moving northward at
20m/s
3. A 40,000g fisherman moving southward
at 2m/s
COLLISIONS
There are two types of collisions:
1. Elastic collision:
2. Inelastic collision:
CONSERVATION OF
MOMENTUM
The law of conservation of
momentum states that: momentum
can neither be created nor destroyed.
It is transferred from one object to
another.
This means that during collision, the
sum of momentum before collision is
equal to the sum of momentum after
collision.
Example
A 2kg clay ball moving at 12m/s strikes a
5kg metal ball. The two balls stick
together and move. Calculate the
velocity with which the two balls move.
exercise
2. IMPULSE
A force applied on an object can produce motion or change the motion of a moving object.
If the force is applied in the same direction as the object’s motion, there is an increase in velocity of the object.
If the force is in the opposite direction, the object slows down.
This force is applied in a certain time interval.
The amount of force multiplied by the time in which the force is applied is called impulse. It results in change of velocity.
• Impulse is change in momentum
Impulse is denoted as force x time (Ft)
Therefore:
Ft = mv – mu
Where:
Ft = impulse (… which is force x time)
m = mass
v = final velocity
u = initial velocity
Example
A 5kg solid ball is moving at 12m/s. A force is applied and its speed reduces to 6m/s.
a. Calculate the momentum of the ball before the force is applied.
b. What is the momentum after the force is applied?
c. Calculate the impulse in this situation.
d. If the force was applied for 5s, what is the magnitude of the force?
Exercise