• (I) A 75.0-kg firefighter climbs a flight of stairs 28.0 m high. How much work does he do?

• (I) The head of a hammer with a mass of 1.2 kg is allowed to fall onto a nail from a height of 0.50 m. What is the maxi- mum amount of work it could do on the nail? Why do people not just "let it fall" but add their own force to the hammer as it falls?

• (II) What is the minimum work needed to push a 950-kg car 710 m up along a 9.0 incline? Ignore friction.

• (I)At room temperature, an oxygen molecule, with mass of 5.31 * 10-26kg, typically has a kinetic energy of about 6.21 * 10-21J. How fast is it moving?

• 17.(I) How much work is required to stop an electron Am = 9.11 * 10-31kg.) which is moving with a speed of 1.10 * 106ms?

• (II) Two bullets are fired at the same time with the same kinetic energy. If one bullet has twice the mass of the other, which has the greater speed and by what factor? Which can do the most work?