Question

1) A car is driving along the freeway.

Estimate the ratio ?r of its kinetic energy to its rest energy.

?=

2)

Suppose that you have found a way to convert the rest energy of any type of matter directly to usable energy with an efficiency of 57.0%. How many liters of water would be sufficient fuel to very slowly push the Moon 2.30 mm away from the Earth? The density of water is ρwater=1.00kg/liter, the Earth's mass is Mearth=5.97×1024 kg, the Moon's mass is Mmoon=7.36×1022 kg, and the separation of the Earth and Moon is dE,M=3.84×108 m.

water: Liters

3)

A recent home energy bill indicates that a household used 465 kWh (kilowatt‑hour) of electrical energy and 185 therms for gas heating and cooking in a period of 1 month. Given that 1.00 therm is equal to 29.3 kWh, how many milligrams of mass would need to be converted directly to energy each month to meet the energy needs for the home?

mass needed:mg

4)

Estimate the difference Δ?diff in a 15000-s time interval as measured by a proper observer and a relative observer traveling on a commercial jetliner.

Δ?diff= s

Answer 1