Transcript Document

Relative Motion
• Example
Outline
Remember
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r  r  R
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v  v  V
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a  a
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Ex 1: Two cars are moving towards one another. Car 1 is
moving at v1=20m/s and Car 2 at v2=30m/s.
a) What is the relative speed between the cars ?
b) How does it differ if Car 1 was stationary and Car 2
moving at 50m/s ?
Ex 2: The cops are chasing a bank robber. Driving at
50m/s they fire a bullet to shoot out his tire. If the gun fires
the bullet at 300m/s, what is the bullet’s speed as
measured by a TV camera crew parked beside the road?
Ex 3: The cops are chasing a bank robber. Driving at
50m/s they fire a bullet to shoot out his tire. If the gun fires
the bullet at 300m/s, and the bank robbers are getting
away at 60m/s, what is the speed of the bullet with respect
to their car is it goes by them?
Ex 4: A boat takes 3.0h to travel 30km down the river and
5.0h to return. How fast is the river flowing ?
Ex 5: A rescue plane is flying 500m above ground level at
a speed of 40m/s.
a) Where, relative to a group of stranded hikers below,
should it drop the parcel so that it lands at their position?
b) Where will the parcel land with respect to the plane ?
For Next Class
• Read 12.3-12.4
Try Chapter 6 # 14, 15, 17