Solution :
Given
Diameter of the roulette ball = 30 cm
The speed ball spun at the beginning = 150 rpm
The speed of the ball during a period of 5 seconds = 60 rpm
Therefore, change of speed in 5 seconds = 150 - 60
= 90 rpm
Therefore,
90 revolutions in 1 minute
or In 1 minute the ball revolves 90 times
i.e. 1 min = 90 rev
60 sec = 90 rev
1 sec = 90/ 60 rec
5 sec = 
= 75 rev
Therefore, the ball made 75 revolutions during the 5 seconds.
Answer:
2.28
Explanation:
From mirror formula,
1/f = 1/u+1/v .......... Equation 1
Where f = focal length of the mirror, v = image distance, u = object distance.
Note: The focal length mirror is positive.
make v the subject of the equation,
v = fu/(u-f)............ Equation 2
Given: f = 2.5 cm, u = 1.4 cm
Substitute into equation 2
v = 2.5(1.4)/(1.4-2.5)
v = 3.5/-1.1
v = -3.2 cm.
Note: v is negative because it is a virtual image.
But,
Magnification = image distance/object distance
M = v/u
Where M = magnification.
Given: v = 3.2 cm, u = 1.4 cm
M = 3.2/1.4
M = 2.28.
Thus the magnification of the tooth = 2.28.
Explanation:
We have,
Surface area, 
The current varies wrt time t as :
(a) At t = 2 seconds, electrical charge is given by :
(b) Current is given by :
Instantaneous current at t = 1 s is,
(c) Current is, 
Current density is given by electric current per unit area.
Therefore, it is the required explanation.
Answer:
See Explanation Below
Explanation:
This question is incomplete.
I'll answer this question on general terms. You'll get your result if you apply the steps I'll highlight below.
To start with; what's Ampere law;
It states that for any closed loop path, the sum of the length elements times the magnetic field in the direction of the length element is equal to the permeability times the electric current enclosed in the loop.
The simple translation of this law is that, the sum of current in the close loop gives us the desired result.
Rephrasing your question;
Three currents, (I1 = +3A, I2 = +4A and I3 = -5A) are passing through a surface bounded by a closed path. The currents have different values and directions. According to Ampere’s law, what is the value of I on the right side of this equation?
First, we take note of the signs in front of the given currents.
The negative sign in front of I3 means that; it is moving in opposite direction of I1 and I2.
To calculate the value of I.
The value of I is the sum of the three currents:
i.e. 3A + 4A - 5A
I = 2 A
E concave mirror because it reflects the light
