Momentum and Its Conservation chapter 9 From our textbook Pages
Momentum Commonly used in terms of sports (i.e. The team has a lot of momentum before the big championship game) The team with momentum is “on the move” and will be hard to defeat.
Momentum Momentum is also a physics term. Momentum- the quantity of motion that an object has; All objects have mass, so if an object is moving, it has momentum (“mass in motion”)
The amount of momentum an object has is dependent on two variables: MASS- How much is moving (weight) VELOCITY-How fast the it is moving (speed)
Momentum Equation The momentum of an object is equal to the mass of the object times the velocity of the object Momentum = Mass times Velocity
IMPULSE The product of the average force and the time interval over which it acts. Unit of measurement is Newton-second (N * s)
The impulse on an object is equal to the change in momentum that it causes. Also Known As…
Impulse-Momentum Theorem Impulse = Momentum
Using the Impulse- Momentum Theorem in real life: Example: If a car is traveling at a fast speed and is suddenly stopped by a thick brick wall, how will its momentum and impulse affect it?
An impulse is needed to bring the driver’s momentum to zero. What can be used to decrease the force exerted on the driver?
An AIR BAG is used to reduce the force exerted on the driver by greatly increasing the length of time the force is exerted.
To Explain: The initial velocity is the same with or without the airbag. The air bag is used to reduce the force by increasing the time it takes the driver to hit the steering wheel.
It’s time to go to work: What is the momentum of a 16 kg bowling ball rolling at 4 m/s? mmomentum = mass * velocity What we know: M = 16 kg V = 4 m/s 16 kg * 4 m/s = 64 kg * m/s = 64 N
More Fun Work: Multi-Step Problem! A. What is the momentum of a 50 kg box that moves 8 m/s across a table? What we know: M = 50 kg V = 8 m/s Momentum = 50 kg * 8 m/s = 400 N
B. The moving box hits a pillow and stops in.5 seconds. What is the average force it exerts on the pillow? ***remember** F (delta) t = m*v What we know: t = 0.5 s M = 50 kg V = 8 m/s F (0.5s-0s) = 50 kg * 8 m/s F (0.5s) = 400 N F = 800 N
C. What average force does the pillow exert on the box? 8800 N The same force used to stop the box The same equation is used
9.2 The Conservation of Momentum Pages
Two- Particle Collision! According to Newton’s third law of motion, if two balls collide, despite different velocities and sizes, the forces exerted on each other will be equal and opposite.
Two- Particle Collision! During the collision, the two balls quickly exert a force on the other. The time intervals over which the forces are exerted are the same so they must be equal in magnitude but opposite in direction.
It’s Time to go to Work! Multi-step problems A 10 kg monster walking 1 m/s eats a 1 kg monster at rest. (A.) What is the speed of the bigger monster immediately afterwards? 10 kg * 1 m/s = 10 kg * m/s 1 kg * 0 m/s = 0 kg * m/s 10 kg * m/s (10 kg + 1 kg) * v = 10 kg * m/s v = 10/11 m/s
(B.) What would its speed be if the smaller monster were walking toward the bigger one 8 m/s? 10 kg * 1 m/s = 10 kg * m/s 1 kg * 8 m/s =- 8 kg * m/s 2 kg * m/s 11 kg * v = 2 kg * m/s v = 2/11 m/s
The End. Mr. Arbo! Give me an A!