A bullet fired into a target loses half of its velocity after penetrating 3 cm. how much further it will penetrate before coming to rest assuming that it faces constant resistance to motion

Question

Malcolm Lam

Physics

20 May, 10:29

A bullet fired into a target loses half of its velocity after penetrating 3 cm. how much further it will penetrate before coming to rest assuming that it faces constant resistance to motion

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Flopsy · Answer 1

The bullet's kinetic energy just as it hits the target is (1/2) (mass) (speed in air) ².

After 3 cm, its speed is reduced to half, so its KE is (1/2) (mass) (1/2 speed in air) ².

That's only 1/4 of its original KE. It lost 3/4 of its energy so far.

As it tears through the target, the force against it is constant. So the energy

taken away from it is (whatever the force is) x (the distance it travels).

It lost 3/4 of its energy in 3 cm. So it's losing 1/4 of its energy each centimeter,

and it has only 1 more cm to go before it stops completely.