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Under the assumption that the three rocks are dropped from the same height, they will hit the ground at the same speed. The gravity of Earth is virtually the same for any object that is small compared to the size of the Earth. The acceleration will change with the distance from the Earth, but this change is so small for the range of heights we work with (consider the range of heights from sea level to the tip of Mount Everest) that we can take the average value and assume it to be constant. This constant value of acceleration due to Earth's gravity is 9.80665m/s²
Because the objects fall under the same constant acceleration, they will hit the ground at the same speed.
Answer:
a) in the upper position. b) in the lower position. c) in the lower position. d) in the upper position. f) Its kinetic and potential energy will be 0, but the energy is transferred to the element or body that stopped the movement of the pendulum
Explanation:
In the attached image we have the sketch of a pendulum system.
A) The potential energy is maximum when the pendulum is in the upper position (image, fig 1) because the elevation (h) is maximum with respect to the reference point.
B) the potential energy is minimum when the pendulum is in the lower pasition (image, fig 2) because the elevation (h) is cero with respect to the reference point.
Note: When the pendulum is coming down the potential energy is transforming in kinetic energy.
C) The kinetic energy is maximum when the pendulum is in the lower position (image, fig 2), because the potential energy has been transformed in kinetic energy.
D) The kinetic energy is maximum when the pendulum is in the upper position (image, fig 1) because at this moment the pendulum is at rest it means its velocity is 0. We know that the kinetic energy depends on the velocity.
f) The energy is transferred to the element or body that stopped the movement of the pendulum