An experiment is conducted to determine how the arm length of a pendulum affects its period. the
experimental design calls for varying the length of the arm and the mass of the bob. which is true
about this experiment, based on good experimental design?
only the mass should be changed. the arm length should remain the same
the force applied to the mass should be varied for each trial
the material the arm is made of should be varied for each trial.
only the arm length should be changed. the mass should remain the same.

Crowbar of 5 metre is used to lift an object of 800 metre if the effort arm is 200cm calculate the force applied

An internally reversible refrigerator has a modified coefficient of performance accounting for realistic heat transfer processes of where qin is the refrigerator cooling rate, qout is the heat rejection rate, and is the power input. show that copm can be expressed in terms of the reservoir temperatures tc and th, the cold and hot thermal resistances rt, c and rt, h, and qin, as where rtot rt, c rt, h. also, show that the power input may be expressed as 1.39 a household refrigerator operates with cold- and hot-temperature reservoirs of tc 5 c and th 25 c, respectively. when new, the cold and hot side resistances are rc, n 0.05 k/w and rh, n 0.04 k/w, respectively. over time, dust accumulates on the refrigerator’s condenser coil, which is located behind the refrigerator, increasing the hot side resistance to rh, d 0.1 k/w. it is desired to have a refrigerator cooling rate of qin 750 w. using the results of problem 1.38, determine the modified coefficient of performance and the required power input w under (a) clean and (b) dusty coil conditions. internally reversible refrigerator qout qin w high-temperature reservoir low-temperature reservoir th th, i tc, i tc high-temperature side resistance low-temperature side resistance w qin th tc qinrtot tc qinrtot copm tc qinrtot th tc

What is the momentum of a 2 kg object moving at 15 meters per second