Which optical device can focus light to a point through reflection?
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Answer:
Check Explanation.
Explanation:
At rest, the car had zero kinetic energy, that is K(rest) = 0. The kinetic energy of the car when the car moved, k(moved) can be calculated by using the work- energy relationship that is;
Work, W= k(moved) - k(rest).
k(moved) = work, W + k(rest).
[Recall that k(rest) = 0]. Therefore, k(moved) = work, W.
{Two Important equations to note are (1). Work, W=( 1/2) mass,m × (speed, V)^2 and (2). Power, P = work,W/ time,t}.
Hence, k(moved) = ( 1/2) mass,m × (speed, V)^2 ---------------------------(1).
Since, power, P= W/t -----------------(2).
Then, equation (2) becomes;
Power, P = m × v^2/ 2 × t.
Making, speed, v the subject of the formula, we have;
v = [(2 × P × t)/ m]^ 1/2. ---------------(3).
Another thing we have to remember is the formula for speed which is the change in distance with time that is; ds/ dt.
Therefore, ds/ dt = [(2 × P × t)/ m]^ 1/2.
ds/dt = [(2 × P)/ m]^ 1/2 × t^ 1/2 ------(4).
Then, the integration of the equation (4) above will give us;
s = ( 8P 9m )^ 1/2 × t^ 3/2 .
(Check attachment for more).
The resistance of a conductor is given by
where L is the length of the wire,
the resistivity of the material and A the cross-sectional area.
We can see that if all the other quantities do not change, if the new length of the conductor is 4 times the original length:
, then the new resistance is also 4 times the original value:
where L is the length of the wire,
We can see that if all the other quantities do not change, if the new length of the conductor is 4 times the original length: