Which of the following is a contact force? O A. Electrical force
O B. Friction
O C. Magnetic force
O D. Gravity

Ammonia enters the expansion valve of a refrigeration system at a pressure of 10 bar and a temperature of 18oc and exits at 6.0 bar. the refrigerant undergoes a throttling process. determine the temperature, in oc, and the quality of the refrigerant at the exit of the expansion valve.

Agroup of students were investigating the force of gravity. they began by dropping a foam ball from a height of 3 meters into a bucket of sand. the ball hit the sand in 0.306 seconds. they dropped additional balls of approximately the same diameter, but of different masses. here is the data they collected. based on this experiment and the collected data, what would their conclusion be?

A100-watt light bulb illuminates a solar cell. the electricity from the solar cell operates a water pump that delivers 1 watt of power. what is the efficiency of the system?