Homework Help: Physics

Posted by J on Saturday, September 18, 2010 at 7:11pm.

A wooden boxcar is moving along a straight railroad track at speed v1. A sniper fires a bullet (initial speed v2) at it from a high-powered rifle. The bullet passes though both lengthwise walls of the car, its entrance and exit holes being exactly opposite each as viewed from within the car. From what direction, relative to the track, is the bullet fired? Assume that the bullet is not deflected upon entering the car, but that its speed decreases by 20%. Take v1=85km/hr and v2 = 650 m/s.

Physics - bobpursley, Saturday, September 18, 2010 at 7:26pm
well, exactly opposite.That means the time the bullet went across the car, the train advanced the same distance as the angle of the bullet would have advanced.

Assume Theta is the angle the bullet entered.

Hmmmm. to figure the time the bullet took to cross the car, one needs to know the width of the car.
distance the car advanced:
distance=bulletspeed*time*sinTheta

Now the train: it advanced
distance=trainspeed*time
set them equal.
bulletspeed*sinTheta=transpeed*time

theta=arc sin (trainspeed/bulletspeed)
bullet speed is .8 of 650 Be certain to change km/hr to m/s
Physics - Anonymous, Sunday, September 19, 2010 at 6:36pm
What?
Physics - Anonymous, Thursday, October 13, 2011 at 5:16pm
I'd love to know where this train came from...

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