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<span>In this situation when using newton's third law, the floor is very rigid and thus when we fall the floor applies
the same amount of force on us with which we were falling on it. The rigidness of the concrete floor makes it difficult for it to absorb some of our force. On the other hand sand is not rigid on impact sine it changes its shape while it absorbs a
large amount of our falling force and a small fraction of this
force is applied on is. That is why we don't get hurt</span>
Answer:

Explanation:
Let assume that cooling water works under a pressure of 1 atmosphere. The time required to boil half of the water is determined by the First Law of Thermodynamics:
![\dot Q \cdot \Delta t = m \cdot [c_{p,w}\cdot (T_{2}-T_{1})+h_{fg}]](https://tex.z-dn.net/?f=%5Cdot%20Q%20%5Ccdot%20%5CDelta%20t%20%3D%20m%20%5Ccdot%20%5Bc_%7Bp%2Cw%7D%5Ccdot%20%28T_%7B2%7D-T_%7B1%7D%29%2Bh_%7Bfg%7D%5D)
![\Delta t = \frac{m\cdot [c_{p,w}\cdot (T_{2}-T_{1})+h_{fg}]}{\dot Q}](https://tex.z-dn.net/?f=%5CDelta%20t%20%3D%20%5Cfrac%7Bm%5Ccdot%20%5Bc_%7Bp%2Cw%7D%5Ccdot%20%28T_%7B2%7D-T_%7B1%7D%29%2Bh_%7Bfg%7D%5D%7D%7B%5Cdot%20Q%7D)
![\Delta t = \frac{(2.25\times 10^{5}\,kg)\left[\left(4.186\,\frac{kJ}{kg\cdot ^{\textdegree}C} \right)\cdot (100\,^{\textdegree}C - 10\,^{\textdegree}C)+2256.5\,\frac{kJ}{kg} \right]}{200000\,kW}](https://tex.z-dn.net/?f=%5CDelta%20t%20%3D%20%5Cfrac%7B%282.25%5Ctimes%2010%5E%7B5%7D%5C%2Ckg%29%5Cleft%5B%5Cleft%284.186%5C%2C%5Cfrac%7BkJ%7D%7Bkg%5Ccdot%20%5E%7B%5Ctextdegree%7DC%7D%20%5Cright%29%5Ccdot%20%28100%5C%2C%5E%7B%5Ctextdegree%7DC%20-%2010%5C%2C%5E%7B%5Ctextdegree%7DC%29%2B2256.5%5C%2C%5Cfrac%7BkJ%7D%7Bkg%7D%20%5Cright%5D%7D%7B200000%5C%2CkW%7D)

Answer: A) Transformer
Explanation: A Transformer is an apparatus, device or a component in a system that is used to convert high voltage into low voltage. It is used to either increase or decrease the voltage of an alternating current.
A transformer uses the basic principle of electro magnetic induction, having two or more coils, the voltage is changed from one coil to another but with thesame frequency as alternating current energy passes through them.
Explanation:
velocity = wavelength × frequency
3×10⁸ = 400/10⁹ × frequency
frequency = 3 × 10¹⁵ /400
frequency = 75×10¹¹Hz