p11 dynamics 3 - momentum and impulse...
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P11 Dynamics 3 Momentum and Impulse Bundle.notebook
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Momentum
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Momentum
The equation for momentum is:
Momentum is a physics term that refers to the quantity of motion that an object has. Sometimes it is defined as "inertia in motion" or "mass in motion."
The amount of momentum which an object has is dependent upon two quantities: mass (how muchstuff is moving) and velocity (how fast and in which direction the stuff is moving).
p momentum
Momentum is a vector quantity!
direction of motion
direction of momentum
direction of momentum
direction of motion
p = mv
m mass v velocity
kg
P11 Dynamics 3 Momentum and Impulse Bundle.notebook
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A taxi possesses a certain amount of momentum, p. What would be the taxis's new momentum if...
a) its velocity were doubled?b) its velocity were halved?c) its mass were doubled (by adding passengers)d) both its velocity and its mass were doubled?
Sample Problem p = mv
P11 Dynamics 3 Momentum and Impulse Bundle.notebook
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Example
Calculate the momentum of a 1200 kg car travelling at 90.0 km/h north.
P11 Dynamics 3 Momentum and Impulse Bundle.notebook
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Check Your Understanding
Which has more momentum, a falling raindrop or a transport truck parked along the side of the road?
P11 Dynamics 3 Momentum and Impulse Bundle.notebook
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Check Your Understanding
Calculate the momentum of a 0.160 kg cricket ball that has a velocity of 110 km/h.
P11 Dynamics 3 Momentum and Impulse Bundle.notebook
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J = Force x Time
A force acting for a given amount of time will change the velocity of the object. If the object's velocity changes, then the object's momentum will also change.
Example
In football, the defensive player applies a force for a given amount of time to stopthe momentum of the offensive player
with the ball.
Impulse, J, is equal to an object's change in momentum.
It is also equal to the product of force and time.
Δp = mΔv
Δp = m(vf vi)
J = FΔt
Change in Momentum and Impulse
Impulse(When Push Comes to Shove)
J = Δp
P11 Dynamics 3 Momentum and Impulse Bundle.notebook
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Change in Momentum
Change in velocity causes change in momentum
This product is referred to as the Impulse
P11 Dynamics 3 Momentum and Impulse Bundle.notebook
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Impulse
Change in Momentum and Impulse are equivalent:
an impulse of 1Ns will provide a change in momentum of 1 kgm/s
P11 Dynamics 3 Momentum and Impulse Bundle.notebook
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A large impulse results if:
a) a large force acts over a short time interval.b) a small force acts over a long time interval.
J = FΔt J = FΔt
FΔt = mΔv
FΔt = m(vf vi)
(This is equation represents Newton's second law of motion.)
Understanding Car Crashes (When Physics meets Biology)
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Application
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Collisions
Collisions usually occur in a short time; force changes quickly
The area of the graph represents the impulse
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Example 1
An egg when thrown against a brick wall will break; however, an egg thrown at the same speed into a sagging sheet will likely survive. Explain why using the concepts of impulse and momentum.
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Example 2
A tennis player hits a ball with a racket, giving it a speed of 43 m/s. If the ball has a mass of 0.085 kg and is in contact with the racket for 4.5 x 103 s, what is the average force exerted on the ball by the racket?
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Newton's Cradle
Netwon's cradle is a device that demonstrates conservation of momentum and energy. It is constructed from a series of pendulums (usually 5) abutting one another. Each pendulum is attached to a frame by two strings of equal length angles awayed from each other. This string arrangement restricts the pendulums' movement to the same plane.
It has been a popular desk toy since being invented, named and produce in 1967 by Simon Pebble. At first a wood cradle version was sold by Harrods of London, and later a chrome design was created by sculptor Richard Loncraine.
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Video Clip
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Sample Problems1. Two cars of equal mass are traveling down King Avenue with equal velocities. They both come to a stop over different intervals of time. The ticker tape digrams for each car are shown below.
a) At which point does each car begin to experience the impulse?
b) Which car (A or B) experiences the greatest acceleration? Justify your answer.
c) Which car experiences the greatest change in momentum? Justify your answer.
d) Which car experiences the greatest impulse? Justify your answer.
Momentum and Impulse
P11 Dynamics 3 Momentum and Impulse Bundle.notebook
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Check Your Understanding
A 0.15 kg cricket ball is approaching a bat with a speed of 95 km/h. After it is hit by the bat, it has a speed in the opposite direction of 115 km/h. The interaction between the bat and the ball lasted 0.015 s.A) what was the change in momentum of the ball?B) What impulse was applied to the ball?C) What was the average force exerted on the ball?
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Module Summary