Is my steps correct.pls help .thank you.

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# Question

# Answer

It is incorrect because the question says the KE is reduced by 75% but your working shows that you have reduced speed by 75% . The reduction % in speed is what you need to find. Instead your end result is finding the % decrease in the KE.

Information from first line gives you:

KE = (1/2) mv^{2 } (formula for kinetic energy and it shows the direct proportion relationship, ie,

when speed v increases, v^{2 } increases, KE increases, when v decreases, v^{2}

decreases, KE decreases.)

So second line says KE decreases by 75% of its original value,

This means new KE = 0.25 (1/2) mv^{2. } ( (1/2)m is a constant, so you do not have to bother about it)

=> New KE = (0.5v)^{2} (1/2)m

=> New speed has decreased from v to 0.5v

So % of reduction in v is [(v-0.5v) / v] x 100% = 50%

The first attempt in the earlier solution, I made a mistake of skipping a step…so I took the reduction in v^{2} instead of v = speed.

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