Answer:
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Explanation:
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Answer:
21.2 m
Explanation:
The current in the wire is given by Ohm's law:
where V is the voltage of the battery and R is the resistance of the wire.
The resistance of the wire is directly proportional to the length of the wire, so we can write:
where k is a constant and L is the length of the wire. Substituting into the first equation,
We can rewrite this equation also as
where the term on the left is a constant (because the voltage of the battery does not change). So, we can write:
where:
is the current in the first situation
is the length of the wire in the first situation
is the current in the second situation
is the length of the wire in the second situation
Re-arranging the formula, we can find the value of L2:
Answer:
The answer is t = 23.81 s
Explanation:
A car in this question means those partition that make up the train
Let denote the the of each car as Z
The equation of motion that has to do with distance is given as
S = ut + (1/2)at²
Where u = initial velocity = 0
t = time = 9 s
Substituting these values we have
Z = (1/2) a(9)²
= 40.5 a
making acceleration the subject we have that a = Z / 40.5
Let us denote the length of the 7th car as =7Z
Considering the distance at the 7th car we have
S₇ = ut₇ + (1/2)at²₇
Where u = initial velocity =0
Substituting values we have
7Z = (1/2)(Z/40.5)(t₇)²
7 = {1/2 ×40.5}(t₇)²
t₇² = 7 × 2 × 40.5
t₇² = 567
t₇ = 23.81 s
