While Robert was helping his father in the garden, he pushed a shovel into the ground to dig a hole in the dirt. He picked up a
shrub, carried it to the hole, and held it while he lowered it into the hole. During which parts of this process does Robert NOT do work? Choose the two statements that apply.
A. He pushed a shovel into the ground to dig a hole.
B. He picked up a shrub.
C. He carried it to the hole
D. He held it while he lowered it into the hole
Work done is given by the change in kinetic energy of an object
The kinetic energy of the shovel, the shrub, and in Robert's movement were changed, therefore, work is done in the given processes,
Reason:
Work is done when the total energy of object is affected by the application of force on the object over a distance
Therefore;
In option <em>A</em>, pushing the shovel into ground (to dig out the dirt) the requires the application of a force (push) over a distance, (into and out of the ground) therefore work is done
In option <em>B</em>, picking the shrub up gives it gravitational potential energy, therefore, work is done
In option <em>C</em>, carrying the shrub to the hole does visible work
In option <em>D</em>, holding the shrub while lowering it into the hole does work by preventing the shrub from falling randomly
Therefore, <u>work is done in the given processes</u>
The dynamo has a wheel that touches the back tyre. As the bicycle moves, the wheel turns a magnet inside a coil. This induces enough electricity to run the bicycle's lights. The faster the bicycle moves, the greater the induced voltage - and the brighter the lights.
