https wwwyoutubecomwatchvhTZIkpppuw A truck rolling down a hill has more momentum than a roller skate with the same speed But if the truck is at rest and the roller skate moves then the skate has more momentum Moving objects can have a large momentum if it has a large mass a high sp ID: 437508
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Slide1
MOMENTUM
https://
www.youtube.com/watch?v=hTZI-kpppuwSlide2
A truck rolling down a hill has more momentum than a roller skate with the same speed. But if the truck is at rest and the roller skate moves, then the skate has more momentum. Moving objects can have a large momentum if it has a large mass, a high speed or both.
8.1
Momentum
Can you think of a case when this truck and roller skate would have the same momentum?Slide3
Sample Problem 1Which has more momentum? A pick up truck traveling at 60 mph or a pick up truck traveling at 100 mph?Which has more momentum? A pick up truck or a smart car? Why?Slide4
Practice Problem #2An ostrich with a mass of 146kg is running to the right with a velocity of 17m/s. Find the momentum of the ostrich.Slide5
IMPULSE
https://
www.youtube.com/watch?v=s6QR0KdyTFYSlide6
Which one would you prefer to hit? A hay stack or a concrete wall? Slide7
MOMENTUM IMPULSE
Combining the twoSlide8
Sample Problem 3A 1400kg car is travelling westward at a velocity of 15m/s, when it veers off the road and collides with a pole and is brought to rest in 0.30s. How much force is exerted on the car during the collision?Slide9
4. Although
it cannot sustain its top speed for more than 8.65 s, the cheetah can run a distance of 274 m during that time. If a cheetah with a mass of 50.0 kg is moving north at its top speed, what is its momentum? First find velocity.Slide10
Summary
Physics of Car Crashes
hewitt
drew itSlide11
And now we have an answer to our the question we started with today… Why is it important to “follow through”…
If you want to increase the momentum of an object you have to apply the greatest force possible for as long as possible.
Swinging as hard as possible for as long as possible will give the ball the most momentum.Slide12Slide13
Khan Academy Tutorialhttp://www.youtube.com/watch?v=XFhntPxow0USlide14
If momentum changes then either the mass, velocity or both have changed. In most cases the velocity changes. And we learned from previous units if you have a change in velocity then the object is
ACCELERATING
We know that
ACCELERATIONS
are produced by
FORCES
.
So the greater the
FORCE
on
an object, the greater
its
ACCELERATION
so
the greater its change in velocity and therefore the greater its change in MOMENTUM.
8.2
Impulse Changes MomentumSlide15
Stopping Time and DistanceThe amount of stopping time for a vehicle, as well as its stopping distance, is governed by the impulse-momentum theorem.A truck with a heavy load will take longer to stop than the same truck without a load. Slide16
When hitting either the wall or the haystack and coming to a stop, the momentum is decreased by the same impulse.The same impulse does not mean the same amount of force or the same amount of time.
It means the same
product
of force and time.
To keep the force small, we extend the time.
8.2
Impulse Changes Momentum