Momentum Terms
Elastic
Inelastic
Explosive
Impulse
100
We have two terms, vector and scalar. Which would be used to describe momentum
VECTOR!
100
Two carts collide elastically. The total momentum before the collision is 18 kg·m/s. After the collision cart 1 has momentum 7 kg·m/s. Find the momentum of the cart 2.
18 = 7 + p2
p2 = 11 kgm/s
100
A 1200 kg car moving at 20 m/s rear-ends a 1200 kg car moving at rest. The cars lock together. Find the final velocity.
v = 10 m/s
doubled the mass so the velocity is half as fast
100
If an object initially at rest explodes into two pieces, what can you say about the total momentum afterward?
The total momentum after will also be zero
100
What does impulse measure?
** I am not looking for a unit **
impulse measures the change in momentum
200
Momentum is a _________ quantity.
Momentum is a Conserved quantity
200
a. A moving bowling ball hits a tennis ball elastically. Which object experiences the greater force during the collision?
b. If it is Elastic then what will happen after the collision?
a. they are equal !!!!
** Newton's 3rd Law **
b. They will bounce off each other
200
A 3 kg cart moving at 4 m/s sticks to a 2 kg cart at rest. Find their final velocity.
m1v1 + m2v2 = v (m1 + m2)
3(4) + 2(0) = v (3+2)
12 = 5v
v = 2.4 m/s
200
A 10 kg cannon initially at rest fires a 2 kg cannonball at 20 m/s. Find the recoil velocity of the cannon
v (m1 + m2) = m1v1 + m2v2
0 ( 10 + 2 ) = 10 V + 2 ( 20 )
0 = 10V + 40
V = -4 m/s
200
A 1200 N force acts for 0.05 s during a car crash. Find the impulse.
I = F t
I = 1200 (0.05 )
T = 60 kgm/s
300
what two quantities are used to create momentum?
mass and velocity
300
A 2 kg blue cart moving at 6 m/s collides elastically with a stationary 2 kg red cart. Find both final velocities.
blue cart = 0 m/s
red cart = 6 m/s
300
In a perfectly inelastic collision, what happens to the objects after impact?
they stick together
300
Why does a gun recoil backward when fired?
because it is an explosive collision and the two objects (gun and bullet) are separating from each other.
300
Why do airbags increase safety in cars?
because they slow you down over a larger period of time which allows for the force to be smaller.
400
List the units for each of the following quantities:
- Mass - Momentum
- Velocity - Impulse
- Force - Time
- Mass (kg) - Momentum (kgm/s)
- Velocity (m/s) - Impulse (kgm/s)
- Force (N) - Time (seconds)
400
Write the equation for elastic collision
m1v1 + m2v2 = m1v1 + m2v2
400
Write the equation for inelastic collision
m1v1 + m2v2 = v (m1 + m2)
400
Write the equation for explosive collision
v (m1 + m2) = m1v1 + m2v2
400
Write the equation for Impulse
I = F t
500
Final Jeopardy
NAME THAT POKEMON
500
A 0.5 kg ball moving at 10 m/s collides elastically with a stationary ball of 3 kg. After the collision the first ball moves at 2 m/s. Find the second ball’s final velocity.
m1v1 + m2v2 = m1v1 + m2v2
0.5(10) + 3(0) = 0.5(2) + 3(V)
5 + 0 = 1 +3v
v = 1.33 m/s
500
Two football players collide and move together. One has mass 80 kg and speed 5 m/s east. The other has mass 100 kg and speed 3 m/s west. Find their combined final velocity.
m1v1 + m2v2 = v (m1 + m2)
80 (5) + 100 (-3) = v (80 + 100)
400 + -300 = 180V
100 = 180 V
V = 0.56 m/s (east)
*could be - 0.56 if you make east the negative one
500
A 6 kg object initially at rest explodes into two pieces. One 2 kg piece moves right at 12 m/s. Find the velocity of the 4 kg piece.
v (m1 + m2) = m1v1 + m2v2
0 ( 2 + 4 ) = 2 ( 12 ) + 4 V
0 = 24 + 4V
V = - 6 m/s
500
which situation experiences a larger impulse?
- when an egg lands on a pillow
or
- when an egg lands on the sidewalk
the change in momentum (impulse) will be the same cause they both had momentum to start and both end with no momentum.
The force and time is what changes but the impulse will remain the same.