The best answer is letter (A) a double pulley system. Atwood Machine is normally used as a measurement in balancing to object to verify the mechanical law of motion with constant acceleration.
A. Angular momentum is always conserved would be the correct answer.
This is because like linear momentum (mvmv), angular momentum (r×mvr×mv) is a conserved quantity, where rr is the vector from the center of rotation. For a skater holding a static pose, for each particle making up her body, the contribution in magnitude to the total angular momentum is given by mirivimirivi. Thus bringing in her arms reduces riri for those particles. In order to conserve angular momentum, there is then an increase in the angular velocity.
hope this helps!
Does it give you options?
I'm trying to think of something that will give you the biggest bang for your buck, meaning what would give you the most number of energy transformations in their use.
Wind energy uses those great big windmills that transform wind into electrical energy. The wind is caused by the sun (which has nuclear energy, light energy and the earth's rotation which is not related to the sun but is mechanical energy). To start with you use mechanical energy. That energy drives a generator that stores it's energy in a battery. You have changed electrical energy into chemical energy. The batteries, on a calm day take over and provide electrical energy that must be transported to the consumers using it. Proponents of wind energy say that it is pollution free. It's not exactly true. The batteries used have to be manufactured (not a clean industry) and when they wear out, they pollute the environment if they cannot be recharged with new battery plates and acid (chemical).
Added to which wind energy is very noisy (sound energy) which has been linked to serious diseases.
A theory is an explanation that unites the findings of many experiments, and it can be changed when new experimental results need to be explained.
