Now we know that motion is a relative term.So absolute motion has no meaning, right?
So aren’t Galileo’s view that earth moves around sun and the church’s old belief that sun moves around earth actually not equally correct or equally wrong?
this is a question from hc verma’s concept of physics part 1.(from short answer questions)
Deepali Gupta asked
Answer: The state of motion as well as the nature of motion is relative. When we speak about any of these without SAYING any reference, we actually have some reference in mind.
When we say that earth is moving around the sun, it is true wrt sun. But, the actual nature of motion is unpredictable since the sun, the galaxy and all are in a state of motion. So, we can say about the nature of motion only with respect to some reference which is assumed to be at rest.
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A stone tied to a string of length l is whirled around a vertical circle with the other end of the string at the centre. At a certain instant of time the stone is at the lowest position and has a speed u. What is the magnitude of change in its velocity as it reaches a position where the string is horizontal?
Let’s assume that the potential energy at the lowest position be zero. So, when the string is horizontal, the stone has risen by a vertical height l, the length of the string which is also the radius of the vertical circle.
If v is the magnitude of velocity at the horizontal position, then according to the law of conservation of energy,
KE+PE at the lowest position = KE+PE at the horizontal position
From the equation above, v-u can be calculated.
The following links will help you for deeper understanding and you can browse through some solved problems from the topic too.
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A mass 5kg descending vertically,draws up a mass of3kg by means of a light string passing over a pulley.At the end of 4 seconds,the string breaks.How much higher 3 kg mass would go?
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