The result is although the wire's resistivity doesn't change, its resistance does.
Considering the formula for a material's resistance:
R=pL/A
R is directly proportional to L and inversely proportional to A, as can be seen. Be aware that "rho" is a material-specific and intensive attribute (meaning this value will not change if the material is only physically altered). Remember that A = This implies that the relationship between R and the square of r is inverse. When the wire is stretched, the impacts on length are less noticeable than the effects on r. Therefore the wire's resistance increases, but its resistivity stays the same.
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Complete question:
A fireman of mass 80 kg slides down a pole. When he reaches the bottom, 4.2 m below his starting point, his speed is 2.2 m/s. By how much has thermal energy increased during his slide?
Answer:
The thermal energy increased by 3,099.2 J
Explanation:
Given;
mass of the fireman, m = 80 kg
initial position of the fireman, hi = 4.2 m
final speed, v = 2.2 m/s
The change in the thermal energy is calculated as;
ΔE + (K.Ef - K.Ei) + (Uf - Ui) = 0
where;
ΔE is the change in the thermal energy
K.Ef is the final kinetic energy
K.Ei is the initial kinetic energy
Uf is the final potential energy
Ui is the initial potential energy

Answer:
The maximum height could be 10.6 meters.
Explanation:
For this kind of exercise, we use the general principle for conservation of mechanical energy (E) that states:
(1)
That means the mechanical energy an object has on a point 2 should be equal to the mechanical energy on a point 1 plus the energy transformed into heat due friction denoted as Wf (It is negative because is lost). In our case point 1 is the point where the roller coaster begins and point 2 is at the second hill. Tola mechanical energy is the sum of potential gravitational energy and kinetic energy, so (1) is :
with K the kinetic energy and U the potential energy, remember potential energy is mgh and kinetic energy is
with m the mass, v the velocity and h the height, then:
Solving for h_2:


Well you of course have different kinetic energies with the two speeds.
Kinetic energy = (1/2)*mass*velocity^2
The vehicle's mass is the same in both cases, so we can ignore that as well as 1/2 since it's a constant.
So we have (30)^2 vs (60^2)
which is 900 vs 3600
So having 60 mph compared to 30 mph is 4 times the kinetic energy.