Question

The bob of a pendulum swings back and forth with a total mechanical energy of 300 J. What is the kinetic energy of the bob when it is at the lowest point of its trajectory? Assume that friction does not affect the pendulum.

200 J

150 J

300 J

0 J

Answer 1

at the lowest point in the trajector, the kinetic energy of the bob is 300 J.

Explanation:

The total mechanical energy of the bob at any point of its motion is given by

$E=KE+PE$

Where

$KE=\frac{1}{2}mv^2$ is the kinetic energy, where

m is the mass of the bob

v is its speed

$PE=mgh$ is the gravitational potential energy, where

g is the acceleration of gravity

h is the height of the bob, measured with respect to the lowest point of the trajector

In absence of friction, the total mechanical energy E remains constant. So we have:

- When the bob swings upward, the PE increases (because h increases) and the KE decreases (so the speed decreases). At the highest point in the trajector, the speed of the bob is zero (v=0), so its KE is also zero and all the mechanical energy is potential energy: U = 300 J

- When the bob swings downward, the PE decreases (because h decreases) and the KE increases (so the speed increases). At the lowest point in the trajectory, the height has become zero (h=0), so the PE is zero and all the mechanical energy is kinetic energy: KE = 300 J

Therefore, at the lowest point in the trajector, the kinetic energy of the bob is 300 J.

Learn more about kinetic energy:

brainly.com/question/6536722

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