Math Is Fun Forum

LuisRodg

Real Member

Registered: 2007-10-23

Posts: 322

Final velocity?

A 0.145 kg glider is moving to the right on a frictionless, horizontal air track with a speed of 0.770 m/s. It has a head-on collision with a 0.290 kg glider that is moving to the left with a speed of 2.10 m/s. Suppose the collision is elastic.

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I need to find the magnitude of the final velocities of both gliders, however, in an earlier problem they gave you the final velocity of one of the objects but here they dont tell you the final velocity of either one. How can you find this?

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A 20.0 kg projectile is fired at an angle of 60.0 above the horizontal with a speed of 80.0 m/s. At the highest point of its trajectory, the projectile explodes into two fragments with equal mass, one of which falls vertically with zero initial speed. You can ignore air resistance.

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I had to find how far the other projectile landed, which I found to be 849 meters. However, it now asks me to find the energy released from the explosion? How do I do that?

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: Final velocity?

The extra bit of information you need in the first question is that the collision is elastic.
That means that the total (kinetic) energy of the system is the same before and after the collision.
That lets you write another equation and you can solve that along with the one you get from conservation of momentum simultaneously.

The second question wants you to find the kinetic energy that the particle had just before it exploded, then the kinetic energy that both the fragments have just after the explosion (one of them is zero, which makes it easier), then find the difference between them to see how much of it was added by the explosion.

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Why did the vector cross the road?
It wanted to be normal.