# physic problems ?

1. 3. A 0.200 kg air-track glider moving at 1.20 m/s bumps into a 0.600 kg glider at rest.

a.) Find the total kinetic energy after collision if the collision is elastic.

b.) Find the total kinetic energy after collision if the collision is completely inelastic.

Show all your work.

2. 4. An archer pulls a bowstring back 0.440 m, and the spring constant of the bow is 545 N/m.

a.) Find the amount of work the archer did to draw the bow.

b.) Find the speed an arrow of mass 0.060 kg will have when it is shot from the bow.

Assume no losses from friction.

Physics problems**

### 2 Answers

- NCSLv 71 month agoFavorite Answer
1a) If the collision is elastic, the total KE after the collision is equal to the total KE before the collision, which is

KE = ½ * 0.200kg * (1.20m/s)² = 0.144 J

b) If inelastic, then we need to first conserve momentum to find the final velocity:

0.200kg * 1.20m/s = (0.200+0.600)kg * V

V = 0.30 m/s

so

final KE = ½ * 0.800kg * (0.30m/s)² = 0.036 J

2a) For a Hookean spring,

work = ½kx² = ½ * 545N/m * (0.440m)² = 52.8 J

b) KE = 52.8 J = ½ * 0.060kg * v²

and so

v = 41.9 m/s

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Source(s): Please revisit this working: https://answers.yahoo.com/question/index?qid=20200... - 1 month ago
a) total kinetic energy after collision = 1/2 x0.2x1.2x1.2 = 0.144 J.

b) for inelastic collision , after collision V = 0.2x1.2 / 0.8 = 0.3 m/sec

hence kinetic energy after collision is 1/2 x0.8x0.09 = 0.036 J.

4). (a) work done = 1/2 x 545 x.0.44x0.44 = 52.756J.

b) speed of arrow v= sq.root(2W/m) = sq.root( 2x52.756/0.06) = 12 m/ sec.

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