A child does 350 J of work while pulling a box from the ground up to his tree house at a steady speed with a light rope. The tree house is above the ground. What is the mass of the box?
A) 8.9 kg
B) 5.3 kg
C) 6.7 kg
D) 8.0 kg
A
You might also like to view...
In the context of the heat flow in the Sun, briefly explain granulation
What will be an ideal response?
Approximately what proportion of stars have masses lower than the Sun?
A) 90% B) 10% C) 50% D) 70%
Liquid oxygen (LOX) for the Space Shuttle can be stored at 90 K prior to launch in a spherical container 4 m in diameter. To reduce the loss of oxygen, the sphere is insulated with superinsulation developed at the U.S. Institute of Standards and Technology’s Cryogenic Division that has an effective thermal conductivity of 0.00012 W/(m K). If the outside temperature is 20°C on the average and the LOX has a heat of vaporization of 213 J/g, calculate the thickness of insulation required to keep the LOX evaporation rate below 200 g/h.
GIVEN
FIND
- The minimum thickness of the insulation (L) to keep evaporation rate below 0.2 kg/h
ASSUMPTIONS
- The thickness is small compared to the sphere diameter so the problem can be considered one
dimensional
- Steady state conditions prevail
- Radiative heat loss is negligible
SKETCH
What is the mass of 2 moles of carbon dioxide?
a. 88 g b. 80 g c. 64 g d. 56 g