If an object with a mass of $2 k g$ $2 kg$ changes speed from $2 \frac{m}{s}$ $2 m/s$ to $4 \frac{m}{s}$ $4m/s$ , by how much does its kinetic energy change?

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Answer 1 · 2018-06-14T06:02:31

$12$ $12$ Joules

Given: mass $= 2 k g$ $= 2 kg$ , changes speed from $2 \frac{m}{s} to 4 \frac{m}{s}$ $2 m/s " to " 4 m/s$ . Find the $Delta KE$

$KE = 1/2 mv^2$

$Delta KE = 1/2 mv_2^2 - 1/2 m v_1^2$

$Delta KE = 1/2 (2)4^2 - 1/2 (2) 2^2$

The units $1 (kg*m^2/s^2) = 1$ Joule

$Delta KE = 16 - 4 = 12$ Joules

Since the mass stays the same you could have simplified the equation by factoring:

$Delta KE = 1/2 m (v_2^2 - v_1^2)$

$Delta KE = 1/2 (2) (4^2 - 2^2)$

$Delta KE = 16 - 4 = 12$ Joules

If an object with a mass of 2 kg 2kg2 kg changes speed from 2 m/s2ms2 m/s to 4m/s4ms 4m/s, by how much does its kinetic energy change?