Answer:
Explanation:
The wires are in circular shape . They have common center .
magnetic field due to circular wire is given by the formula
B = 
where I is current , r is radius of the coil .
magnetic field due to inner wire
= 
magnetic field due to outer wire
= 
These should be equal and opposite so that by cancelling each other , they create zero field.
= 
I = 16.66 A
Direction of current should be in opposite direction ie anticlockwise when looking from above.
Answer:
7.328m/s
Explanation:
Given parameters:
height of table = 0.68m
final velocity of the ball = 6m/s
Unknown:
Initial velocity of ball = ?
Solution:
To solve this problem, we are going to employ the appropriate motion equation.
We must understand that this fall occurs in the presence of gravity;
V = U + 2gH
Where;
V is the final velocity
U is the initial velocity
g is the acceleration due to gravity
H is the height of the pool table
Since U is the unknown, let us make it the subject of the expression;
U = V - 2gH
U = 6 - (2 x 9.8 x 0.68) = 7.328m/s(deceleration)
Answer:
39.2m/s
Explanation:
The potential energy the book has right before it falls is equal to the kinetic energy in falling.
PE = KE
mgh = (1/2)mv
2gh=v
v=(2)(9.81)(2)
v=39.24m/s
Answer:

The rule for kilometers is that every three seconds between a lightning flash and the following thunder gives the distance to the flash in kilometers.
Explanation:
In order to use the rule of thumb to find the speed of sound in meters per second, we need to use some conversion ratios. We know there is 1 mile per every 5 seconds after the lightning is seen. We also know that there are 5280ft in 1 mile and we also know that there are 0.3048m in 1ft. This is enough information to solve this problem. We set our conversion ratios like this:

notice how the ratios were written in such a way that the units got cancelled when calculating them. Notice that in one ratio the miles were on the numerator of the fraction while on the other they were on the denominator, which allows us to cancel them. The same happened with the feet.
The problem asks us to express the answer to one significant figure so the speed of sound rounds to 300m/s.
For the second part of the problem we need to use conversions again. This time we will write our ratios backwards and take into account that there are 1000m to 1 km, so we get:

This means that for every 3.11s there will be a distance of 1km from the place where the lightning stroke. Since this is a rule of thumb, we round to the nearest integer for the calculations to be made easily, so the rule goes like this:
The rule for kilometers is that every three seconds between a lightning flash and the following thunder gives the distance to the flash in kilometers.
Answer: A crest is the highest point the medium rises to and a trough is the lowest point the medium sinks to. It is also a point on the wave where the displacement of the medium is at a maximum.