Answer: 588 joules
Explanation:
Work is done when force is applied on an object over a distance ( whether vertical or horizontal). It is measured in joules.
Thus, Workdone = Force X distance
- Vertical distance to be moved by the brick = 12 metres
- Mass of box = 5kg
- Acceleration due to gravity when box was lifted represented by g is a constant with value of 9.8m/s^2
Now, recall that Force = Mass x acceleration due to gravity
i.e Force = 5kg x 9.8m/s^2
Force = 49 Newton
So, Workdone = Force X Distance
Workdone = 49 Newton X 12 metres
Workdone = 588 joules
Thus, 588 joules of work was done.
Answer:
AM broadcasts occur on North American airwaves in the medium wave frequency range of 525 to 1705 kHz (known as the “standard broadcast band”). The band was expanded in the 1990s by adding nine channels from 1605 to 1705 kHz.
<h3>Concave or diverging lens is needed correct the vision of a nearsighted person whose far point is 30.0 cm</h3>
<em><u>Solution:</u></em>
Nearsighted person will not be able to see the distant objects clearly
Now, we want the near sighted person to see the distant objects clearly
<em><u>The lens equation is given as:</u></em>

For distant vision, 

The image of 30 cm from eye will be 28.5 cm to left of spectacle lens
Therefore,

From lens equation,

The negative power -3.51 D denotes that a concave or diverging lens is needed
(i)1.5cm
(ii)4.5cm
(iii)10cm