Ccl2f2 is considered to be environmentally safe and is used as a refrigerant. the heat of vaporization of ccl2f2 is 289 j/g. what mass of this substance must evaporate in order to freeze 2 moles of water initially at 20°c? the heat of fusion of water is 334 j/g and the specific heat of water is 4.18 j/g-k.

The answer is  a.first and third quarters 

Answertraveling around a circular trackexplanation"traveling around a circular track" is the best answer as you could be traveling around a circular track at a constant speed. your velocity would therefore have the same magnitude but will always be constantly direction. since acceleration is the rate of change of velocity, the rate of change will only involve the direction of velocity and not the magnitude.wrong choices: "an object at rest" does not accelerate at all"increasing speed while traveling around a curve" means that the acceleration will not be constant due to only change in direction; it will be constant due to both magnitude and direction"an object in free fall" does not necessarily change direction 

Since the pully is a simple machine so the mechanical advantage is a 1