The calculated total mechanical energy will reduce if the oscillation is not perpendicular to the photogate.
The mechanical energy at the lowest position of the pendulum is calculated as follows;
[tex]U = K.E = \frac{1}{2}mv^2[/tex]
let the velocity of the pendulum = vsin(θ)
when the velocity is perpendicular = vsin(90) = v
At any direction different from perpendicular direction, the mechanical energy reduces by;
[tex]\Delta U = \frac{1}{2} mv^2 - \frac{1}{2} m(vsin\theta)^2\\\\\Delta U = \frac{1}{2} m(v^2 - v^2sin^2\theta)\\\\\Delta U = \frac{1}{2} mv^2(1 - sin^2\theta )[/tex]
Thus, the calculated total mechanical energy will reduce if the oscillation is not perpendicular to the photogate.
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