#### Transcript of LPH 105 W15 7.1-3

Impulse - momentum

Main Ideas:

Links Force to momentum, need time of impact (F,t,p)

Key phrases (things to look for)

Forces, time, mass, velocity, IMPULSE,

A 0.145 ball is pitched at 31.0 m/s is hit on a horizontal line drive back at the pitcher at 46.0 m/s If the contact time is 5.00 ms what is the force?

2230 N

b) what is the average force acting on the nail?

A 12 kg hammer strikes a nail at a velocity of 7.5 m/s and comes to rest in a time interval of 8.0 ms.

a) what is the impulse given to the nail?

90 kg m/s

11000 N

A pitcher throws a 0.15 kg ball with an initial speed of 25 m/s. The batter hits with a force of 1500 N for a time of 7.0 ms, how fast does it come back at the pitcher?

45 m/s

A child in a boat throws a 5.3 kg package out horizontally with a speed of 10.0 m/s What is the boats velocity afterward, if it started at rest. Let the mass of child and boat be 70 kg.

-.757 m/s

A 7200 kg railroad car move on a level frictionless track at a speed of 58 m/s. A 2750 kg load is dropped vertically down onto the car. What will be the car's new speed?

An atomic nucleus moving at 333 m/s emits an alpha particle in the same direction as its velocity and the remaining nucleus slows to 275 m/s. How fast will the alpha particle be moving if the initial mass was 222 u?

3490 m/s

42 m/s

How fast would the remaining nucleus be moving if it emitted the alpha particle straight behind it with the same velocity found here?

403 m/s

An object at rest is suddenly broken apart into two fragments by an explosion. One fragment acquires twice the kinetic energy of the other. What is the ratio of their masses?

m1=.5m2

In an explosion 50,000J of energy is released, if only 10% is given to move the only two fragments of non-negligible mass, 10 kg and 25 kg, what are their respective final velocities?

26.7 & 10.7 m/s

**"When doing average force, do I assume the same +/- direction of momentum?"**

**"I am confused about impulses. What does an impulse tell us?"**

"Review example 7-1, if the return volley had the ball initially APPROACHING at a speed of 40 m/s (air resistance slowed it down) and then leaving at a speed of 40 m/s BACK TOWARDS the server. If the contact time is the same, what force was exerted by the player? (should look like '1400 N')"

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