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Taya2010 [7]
2 years ago
15

Lucy and her bike together have a mass of 120kg. She slows down from 4.5m/s to 3.5m/s. How much kinetic energy does she lose?

Physics
1 answer:
vovangra [49]2 years ago
7 0
The kinetic energy of a moving object is given by
K= \frac{1}{2}mv^2
where m is the object's mass and v its velocity.

In our problem, the initial kinetic energy is:
K_i =  \frac{1}{2} m v_i^2 = \frac{1}{2}(120 kg) (4.5 m/s)^2=1215 J

while the final kinetic energy is:
K_f =  \frac{1}{2}mv_f^2 =  \frac{1}{2}(120 kg)(3.5 m/s)^2= 735 J

So, the kinetic energy lost by Lucy and her bike is
\Delta K = K_i - K_f = 1215 J - 735 J = 480 J
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