To determine in which examples of motion a body can be considered as approximately a point object, we analyze the given options based on the concept of a point object in physics.
A point object is an object whose size is negligible compared to the distance it travels, making it easier to analyze motion without considering its dimensions. Let's evaluate each option:
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A railway carriage moving without jerks between two stations:
- In this case, the size of the carriage is negligible compared to the long distance between stations. Therefore, we can consider the entire carriage as a point object since the motion analysis focuses on its center of mass moving smoothly.
- This reasoning aligns with the concept of a point object, hence this example fits the criteria.
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A monkey sitting on top of a man cycling smoothly on a circular track:
- Here, the size of the monkey-man system is small compared to the size of the circular track. Thus, when analyzing the overall motion along the track, they can be approximated as a point object.
- This example also satisfies the condition to be considered a point object because the focus is on the path along the track rather than their individual sizes.
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A spinning cricket ball that turns sharply on hitting the ground:
- The spinning ball's rotation and the change in direction upon impact involve complexities in its motion, such as spin and bounce. These factors require we consider the size and shape of the ball, so it cannot be treated as a point object.
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A tumbling beaker that has slipped off the edge of a table:
- The tumbling motion of the beaker involves rotation where the dimensions and orientation of the beaker are significant. Hence, it cannot be approximated as a point object because its size matters in describing its motion.
We conclude that the correct options are the railway carriage moving without jerks and the monkey sitting on top of a man cycling smoothly, as in both situations, their respective sizes are negligible relative to the distance or path they travel.