Which of the following is true about high-energy mechanical devices? a. they usually need to be kept warm in order to preserve mechanical energy
b. they usually need to be cooled to dissipate thermal energy build- up and prevent damage. c. they usually convent radiant energy into electrical energy
d. during an energy conversion none of the energy is transferred as thermal energy because the devices are free of friction

B. They usually need to be cooled to dissipate thermal energy build-up and prevent damage.

Explanation:

High energy mechanical devices needs to be cooled down because they have moving parts which creates heat which may affect the other electrical and electronic component of the device. Because quality of material changes with the temperature. If high temperature occur might change the shape of that component and may affect the efficiency of the machine.

B.) They usually need to be cooled dissipate the thermal energy build-up and prevent damage

with 5 seconds, no, but over time if the police car stays at 65m/s ad the speeding car stays at 60, then obviously yes, but the answer to your question would be, no.

hope this : )

d) physical means can be used to separate the components of air.