Unit 1 physics ial help please! Watch

Simplysubah
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Please explain me these two. Answers- 5B, 6C
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RogerOxon
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(Original post by Simplysubah)
Please explain me these two. Answers- 5B, 6C
For 6, the ratio of the kinetic energies is 0.9/3.3. As KE is proportional to the square of the speed, the ratio of the speed is the square root of that, i.e. C.

For 5, the energy in a spring is proportional to the spring constant AND the square of the extension:
E=\frac{kx^2}{2}

F=kx

\therefore E=\frac{F^2}{2k}

So, the energy is inversely proportional to the spring constant (for a constant force). Doubling the spring constant will half the energy, i.e. B.

A simple way of seeing this is that the work done is force (which varies linearly) times distance, but doubling the spring constant halves the distance, so halves the stored energy.

P.S. "Please explain these two *to* me"
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Simplysubah
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(Original post by RogerOxon)
For 6, the ratio of the kinetic energies is 0.9/3.3. As KE is proportional to the square of the speed, the ratio of the speed is the square root of that, i.e. C.

For 5, the energy in a spring is proportional to the spring constant AND the square of the extension:
E=\frac{kx^2}{2}

F=kx

\therefore E=\frac{F^2}{2k}

So, the energy is inversely proportional to the spring constant (for a constant force). Doubling the spring constant will half the energy, i.e. B.

A simple way of seeing this is that the work done is force (which varies linearly) times distance, but doubling the spring constant halves the distance, so halves the stored energy.

P.S. "Please explain these two *to* me"
Thank you so much:’)
Please keep helping us this way. So grateful :’)
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