Answer:
The answer is A
Explanation:
Density basically shows the amount of mass per volume of something. You can easily find Density with the equation D=m/v
D= Density
m= mass
v= volume
To solve this problem we will apply the concepts related to volume, as a function of length and area, as of mass and density. Later we will take the same concept of resistance and resistivity, equal to the length per unit area. Once obtained from the known constants it will be possible to obtain the area by matching the two equations:
Mass of copper wire
Density 
Resistively of copper 
Resistance (R) = 0.390\Omega
Volume is defined as,
(1)
We know that,
(2)
Multiplying equation we have
Therefore the length of the wire is 1.68m
The car at 60 kph has 9 times more kinetic energy than the car traveling at 20 kph. This assumes that both cars have the same mass. Kinetic energy depends on the square of thee speed so if one car is going 3 times faster, its kinetic energy will be 3^2 ( = 9 ) greater. The car going at 60 kph will have 4 times the KE of the car going at 30 kph ( again assuming that the cars have the same mass.)
Before 7 after 9. A pH smaller than 7 indicates acidity with 0 being completely acidic. A pH greater than 7 shows alkalinity with 14 being completely alkaline. 7 is neutral. Since NaOH is alkaline, adding it to a neutral substance would increase the pH and it would increase from 7 to 9.
momentum= mass × velocity
p= 50×18
momentum= 900 kg m/s
