Answer:

Explanation:
Given that
J(r) = Br
We know that area of small element
dA = 2 π dr
I = J A
dI = J dA
Now by putting the values
dI = B r . 2 π dr
dI= 2π Br² dr
Now by integrating above equation


Given that
B= 2.35 x 10⁵ A/m³
r₁ = 2 mm
r₂ = 2+ 0.0115 mm
r₂ = 2.0115 mm

By putting the values


Very roughly 7,700 feet ... about 1.5 miles.
Answer:
-6.6 km/h
Explanation:
In 7hr plane travelled 2020km;
For the first 4hr the average speed was 310km/h;
d=st, s=d/t;
Distance covered in first 4h is d = 310km/h×4h = 1240km;
See the image attached for further solution
Answer:
Explanation:
height of pole = 15 ft
height of man = 6 ft
Let the length of shadow is y .
According to the diagram
Let at any time the distance of man is x.
The two triangles are similar

15 y - 15 x = 6 y
9 y = 15 x

Differentiate with respect to time.

As given, dx/dt = 4 ft/s

ft/s