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**Answer:**

t = 1130 s = 18.83 min

**Explanation:**

First, we will calculate the energy required to evaporate 500 g of water:

where,

E = Energy Required for evaporation of water =?

m = mass of water = 500 g = 0.5 kg

L = Latent heat of vaporization of water = 2.26 MJ/kg = 2260 KJ/kg

Therefore,

Now, we will calculate the time required:

where,

t = time = ?

P = Power of kettle = 1 KW

Therefore,

<u>**t = 1130 s = 18.83 min**</u>

**Answer:**

(a) θ= 43.89°

(b)

**Explanation:**

**Ball 1:**

**Ball 2:**

As the collision is elastic, it means that kinetic energy and momentum are conserved. Following that, we apply the law of conservation of energy and momentum:

and

Where u is the velocity before the collision, and v are the velocities after the collision. Both previous equations can be simplified as:

and

This because the two balls have the same mass. We know that the cue ball is deflected and makes an angle of 30°. From conservation in x-direction, we get::

and

Solving we get:

From conservation in y-direction, we get:

From this, we solve this equation system and get the answers. Remember to add 30° to the angle obtained.

b. second

Scientists would have used the theory of relativity when designing their experiment, and design is the second stage of the engineering process.

**Answer:**

**Worldwide Radio Communication**

**Explanation:**

The ionosphere is important because it is through the ionosphere that world wide radio communication is possible.