Calculate the current density needed to `levitate' a copper wire in the earth's magnetic field (that is, the current required for the lorentz force on the wire to be equal to its weight). assume that the wire is at the magnetic equator where the field is horizontal with magnitude 10-4 tesla. take the density of copper to be 8.9 g cm3 .
(b) calculate the power dissipated in the wire per unit volume. will the wire become hot? the resistivity of copper is 1.7 x 108 ω.m and the heat capacity of copper is 385 j kg-1 k -1 .
i have part (a) i just need part (b)
answer to part (a) is j=8.73x10^8 a/m^2.

the minimum constant speed at which she can catch the train is 2.7 m/s

given:

acceleration = 0.6

time = 4.5 s

to find:

velocity = ?

formula used:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

solution:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

v = 0 + (0.6 × 4.5)

v = 2.7 m/s

the minimum constant speed at which she can catch the train is 2.7 m/s

answer: the metamorphic rocks are formed when they are exposed to high pressure and high temperatures. this happens when one of the earth's plates comes in contact with the other plate by traveling in opposite directions, straight into each other or slipping under one another. the friction that is caused by this activity results in   melting of rocks and when it cools they are known as metamorphic rocks. this process needs a controlled amount of pressure and temperature otherwise it may turn into magma.

d. platinum would have the greatest temperature increase because it has the lowest specific heat.

find the surface area of the sphere to the nearest square unit. use a calculator.

a. 254 in.2

b. 64 in.2

c. 127 in.2

d. 1,018 in.2