Both local and global winds are caused by what?
1 answer:
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The resistance of a conductive wire is given by:
where
is the material resistivity
is the wire length
is the cross-sectional area of the wire
The length of the wire is quadrupled, so if we call L the original length and L' the new length, we can write
Similarly, the radius of the wire is doubled (r'=2r), so the new area is
And if we substitute into the equation, we find that the new resistance of the wire is
Therefore, R=R': this means that the resistance of the wire did not change.
where
The length of the wire is quadrupled, so if we call L the original length and L' the new length, we can write
Similarly, the radius of the wire is doubled (r'=2r), so the new area is
And if we substitute into the equation, we find that the new resistance of the wire is
Therefore, R=R': this means that the resistance of the wire did not change.
Answer:
Therefore maximum stretch is y2 = 32.36 m
Explanation:
In this problem let's use the initial data to find the string constant, let's apply Newton's second law when in equilibrium
- W = 0
k Δx = mg
k = mg / Δx
k = 80 9.8 / (30-20)
k = 78.4 N / m
now let's use conservation of energy to find the velocity of the body just as the string starts to stretch y = 20 m
starting point. When will you jump
Em₀ = U = mg y
final point. Just when the rope starts to stretch
= K = ½ m v²
Em₀ = Em_{f}
mg y = ½ m v²
v = √ 2g y
v = √ (2 9.8 20)
v = 19.8 m / s
now all kinetic energy is transformed into elastic energy
starting point
Em₀ = K = ½ m v²
final point
Em_{f} = + U = ½ k y² + m g y
Emo = Em_{f}
½ m v² = ½ k y² + mgy
k y² + 2 m g y - m v² = 0
we substitute the values and solve the quadratic equation
78.4 y² + 2 80 9.8 y - 80 19.8² = 0
78.4 y² + 1568 y - 31363.2 = 0
y² + 20 y - 400 = 0
y = [- 20 ±√ (20 2 +4 400)] / 2
y = [-20 ± 44.72] / 2
the solutions are
y₁ = 12.36 m
y₂ = 32.36 m
These solutions correspond to the maximum stretch and its rebound.
Therefore maximum stretch is y2 = 32.36 m
The amount of heat needed to melt the block of lead is
Explanation:
The amount of heat needed to melt a solid substance already at its melting point is given by the equation
where
m is the mass of the substance
is the specific latent heat of fusion
In this problem, we have a block of lead already at its melting point, . Its mass is
m = 200 g = 0.2 kg
and its specific latent heat of fusion is
Therefore, the amount of heat needed for the block to completely melt is
Learn more about specific heat:
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