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What's the maximum speed?

A compressed spring has 16 J of potential energy. What's the maximum speed it can impart to a 2 kg object?
Answer: 4.0 m/s
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2 Answers

Use energy conservation. When the object reaches its maximum speed, all the potential energy is converted to kinetic energy. So,
(1/2)mv^2 = 16
Plug in m = 2 kg, and solve for v,
v = 4.0 m/s <==Answer
Hi Sun;
A joule is kg-m2/s2.
As Robert explained, the equation is...
kinetic energy=(1/2)mv2
16 kg-m2/s2=(1/2)(2 kg)(x m/s)2
The result we want is m/s.
The unit of kg is in the numerator of both sides of the equation.  These cancel...
16 kg-m2/s2=(1/2)(2 kg)(x m/s)2
16 m2/s2=(1/2)(2)(x m/s)2
16 m2/s2=(x m/s)2
Let's take the square-root of both sides...
4 m/s=x m/s