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Category: Science Homework

If a good absorber of radiant energy were a poor emitter, how would its temperature compare with its surroundings?

Saturday, July 17th, 2010

Solution:

A good absorber of radiant energy, like a black surface, sends to get hot. If it is a poor emitter, that means it will remain hot for a long time. Therefore, an object that is both a good absorber of radiant energy and a poor emitter would tend to be hotter than its surroundings.

How much energy would it take to raise 4 grams of water by 6 degrees Celcius?

Friday, July 16th, 2010

Solution:

Specific heat capacity for water = 4.18 Joules/(gram*degree Celcius)
(how much energy is required per gram per change in degrees C)

mass = 4g
Change in temperature = 6 deg C

energy required = mass * change in temperature * specific heat capacity
= 4g * 6 deg C * 4.18 J/(g*deg C)
= 100.32 Joules

What is the difference between a scalar and vector Quantity?

Friday, July 16th, 2010

Vector quantities have two characteristics: magnitude and a direction. Scalar quantities only have magnitude.