Motion in a vertical circle and conservation of energy
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?
Answer:
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
[latex]\frac{1}{2}mu^{2}=\frac{1}{2}mv^{2}+mgl[/latex]
From the equation above, v-u can be calculated.
[latex]v=\sqrt{u^{2}-2gl}[/latex]
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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Is law of conservation of energy violated here?
“When a body is moving with uniform speed on a rough surface under the application of a constant external force and an equal and opposite frictional force, the work done by both the forces should be equal. as a result, the net work done by both the forces should be zero. however, we find that [...]
Categories: Ask Physics Tags: application, body, frictional force, law, law of conservation, law of conservation of energy, result, uniform motion, uniform speed, work
Interference is in complete agreement to law of conservation of energy
Tilak gurjar posted;
“Interference is in complete agreement to law of conservation of energy. Comment”
Answer:
If there were no interference, the resultant intensity at a point illuminated by two sources will be
I = I1+I2
Due to interference
This shows that energy is conserved even after interference. There is only a redistribution of energy. There is no loss or gain of energy
Categories: OPTICS Tags: answer, conservation of energy, gurjar, intensity, interference, law, law of conservation, law of conservation of energy, loss, redistribution
