## Explosion and Collision

A space probe explodes in flight into three equal portions. One portion continues along the original line of flight. The other two go off in directions each inclined at 60º to the original path. The energy released in the explosion is twice as great as the kinetic energy possessed by the probe at the time of the explosion. Determine the kinetic energy of each fragment immediately after the explosion.

Analyze the problem:

With the word explosion we should know that it could involve conservation of momentum and kinetic energy.

What are the given information?

1. Three fragments of exploded probe that have equal masses
2. Direction of probe is φ=0º with the horizontal.
3. Directions of motion of each fragment after explosion are: fragment 1 (θ1=60º with the horizontal), fragment 2 (θ2=0º with the horizontal), fragment 3 (θ3=-60º with the horizontal).
4. Total energy released during explosion is twice the total kinetic energy of the probe.

What are the needed information?

1. The final kinetic energy for each fragment of the probe immediately after explosion.

SOLUTION:

## Rotating Flywheel

Source: REA’s Problem Solvers Physics by Research and Education Association.

Delivery trucks which operate by making use of the energy stored in a rotating flywheel have been in use for some time in Germany. The trucks are “charged up” before leaving by using an electric motor to get the flywheel up to its top speed of 6000 revolutions per minute. If one such flywheel is a solid homogeneous cylinder of weight 508 kg and diameter 1.8 m, how long can the truck operate before returning to its base for “recharging”, if its average power requirement is 10 HP?

Analyze the problem:

A disk (flywheel) can rotate with maximum angular speed of 6000 revolutions per minute which can provide kinetic energy that allow a truck to move. When there is an average power needed that allow the truck to operate, the truck will be in motion for limited time as the energy eventually will be reduced with time and that will reduce the power (rate of energy consumed per unit time).

What are the given information?

1. Maximum angular speed of the flywheel, ω=6000 revolutions/minute
2. Flywheel shape is cylinder
3. Flywheel mass, M = 508 kg
4. Flywheel diameter, D= 1.8 m
5. Average power needed for the truck , P = 10 horse power

What are the needed information?

1. The average time the truck can operate

SOLUTION: