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

Physics & Space Science

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In the context of the heat flow in the Sun, briefly explain granulation

What will be an ideal response?

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Approximately what proportion of stars have masses lower than the Sun?

A) 90% B) 10% C) 50% D) 70%

Physics & Space Science

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

Physics & Space Science

What is the mass of 2 moles of carbon dioxide?

a. 88 g b. 80 g c. 64 g d. 56 g

Physics & Space Science