The most primitive way to measure a distance travelled in a time period. One dif
ID: 2119524 • Letter: T
Question
The most primitive way to measure a distance travelled in a time period. One difficulty in measuring the speed of a fast- moving bullet is that if a reasonable measurement of distance is selected, the time increment will be small, but if the time increment is reasonable, the distance will be large. In the 1740%u2019s the ballistic pendulum was developed as a solution to this dilemma. In this device, a fast-moving bullet imbeds itself in the wooden %u201Cbob%u201D of a large pendulum, which then swings upward to an angle. If you know the angle, you can work back to find the speed of the bullet.
a) The ballistic pendulum is a two part problem.
First, the fast-moving bullet imbeds itself in the pendulum. Can this process be easily modeled by conservation of energy, or conservation of momentum, or both?
Second, the pendulum swings upward, can this part of the problem be easily modeled as conservation of energy, conservation of momentum, or both?
b) The first bullets that were measured with the ballistic pendulum were musket balls, with a mass of about 30.0 grams. A reasonable velocity for such a bullet would be 215 m/s. If the mass of the pendulum bob was 5.45 kg, what would be the speed of the combined pendulum/bullet mass right after the bullet imbedded in the wood?
c)If the pendulum bob swings on a string that is 0.65 m long, what is the maximum angle that the bob (with imbedded bullet) swings out to (measure relative to its original vertical position)?
Explanation / Answer
A) for the first part ,, conservation of momemtum is valid..
for the second part ,, conservation of energy is valid
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