The answer is to maintain safety.
Kinetic energy and velocity are at zero when the magnets are held apart, and both increase rapidly when they are released and move together. Energy stored in the magnetic field decreases.
The rock's height <em>y</em> at time <em>t</em> is given by
<em>y</em> = 45 m + (7.2 m/s) <em>t</em> - 1/2 <em>g</em> <em>t </em>²
where <em>g</em> = 9.80 m/s² is the magnitude of the acceleration due to gravity. Set <em>y</em> = 0 and solve for <em>t</em> :
0 = 45 m + (7.2 m/s) <em>t</em> - 1/2 <em>g</em> <em>t </em>² → <em>t</em> ≈ 3.9 s
Answer:
The van der wall forces are existed between separate molecules of water but not between the hydrogen and oxygen molecules.
Explanation:
<em>Van der wall forces include repulsion and attraction between the atoms, surfaces and molecules.</em> <em>The intermolecular forces are also included in the van der wall forces. Basically, van der wall forces are the forces that are formed between molecules of the same molecules but not with the different molecules of the same substance.</em> Take water molecules into consideration,<em> van der wall forces exist between the water molecules but these forces are not associated between hydrogen and oxygen molecules. </em>These forces are fragile than ionic bond and covalent bond.