For the cold pack shown below, the temperature on the outside surface has dropped considerably from its initial temperature of 25 °C. Which of the following provides the best explanation for this temperature decrease? A. The cold pack is releasing cold to the surroundings.
B. Ice is beginning to form on the outside of the bag, lowering its temperature.
C. Energy is traveling out of the bag into the surroundings, making the bag colder.
D. The thermometer is measuring the temperature of the surroundings, which is losing energy.

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Explanation:

first let us lay out the formula for potential

and kinetic energy:

pe = mgh

ke = (mv^2)/2

where: m=mass, v=velocity, g=gravitational

acceleration, h=height

calculating for mass using the known values of

pe:

340j = m (9.81 m/s^2) (50ft) (1m/3.28ft)

m = 2.27 kg

the law of conservation of energy states that

energy is neither created nor destroyed. therefore, the change in kinetic

energy from 50 ft to 35 ft would be equal to the change in potential energy

from 50 ft to 35 ft. however it would be opposite in signs since one is losing

while other is gaining.

ke(35ft) – ke(50ft) = - [ pe(35ft) – pe(50ft]

ke(50ft) = 0 since the brick is initially at rest

ke(35ft) = 340j - 2.27kg (9.81 m/s^2) (35ft)

(1m/3.28 ft)

ke(35ft)

= 102.38 j