Answer:
Length = 2.32 m
Explanation:
Let the length required be 'L'.
Given:
Resistance of the resistor (R) = 3.7 Ω
Radius of the rod (r) = 1.9 mm = 0.0019 m [1 mm = 0.001 m]
Resistivity of the material of rod (ρ) = 
First, let us find the area of the circular rod.
Area is given as:

Now, the resistance of the material is given by the formula:

Express this in terms of 'L'. This gives,

Now, plug in the given values and solve for length 'L'. This gives,

Therefore, the length of the material required to make a resistor of 3.7 Ω is 2.32 m.
Answer:
4.163 m
Explanation:
Since the length of the bridge is
L = 380 m
And the bridge consists of 2 spans, the initial length of each span is

Due to the increase in temperature, the length of each span increases according to:

where
is the initial length of one span
is the temperature coefficient of thermal expansion
is the increase in temperature
Substituting,

By using Pythagorean's theorem, we can find by how much the height of each span rises due to this thermal expansion (in fact, the new length corresponds to the hypothenuse of a right triangle, in which the base is the original length of the spand, and the rise in heigth is the other side); so we find:

Answer: 7750 J
Explanation:
Mechanical energy is potential energy added to kinetic energy.
5000 + 2750 J = 7750 J
Answer:
The acceleration would be 3.455.
Linear expansivity, area expansivity and volume or cubic expansivity are