10. Conservation of Energy

A spring-loaded toy gun shoots a $3.0\mathrm{g}$ plastic ball straight up into the air. From the position of the ball when the gun is cocked, with the spring compressed, to the maximum height the ball reaches, is $2.5\mathrm{m}$. If the spring was compressed $2.0\mathrm{cm}$, what is the spring constant of the spring? Ignore air resistance.

Calvin uses a catapult to launch a foam football at Susie. If the ball leaves the catapult at a height of $2.0\mathrm{m}$ and is moving at $15\mathrm{m}/\mathrm{s}$ when it strikes the ground (he missed), how fast was the football moving when it left the catapult? Ignore air resistance.

A toy gun is mounted on a tabletop. It shoots a small plastic ball at $6.0\mathrm{m}/\mathrm{s}$. The ball leaves the toy gun at an angle of 24° above the horizontal, and a height of $83\mathrm{cm}$ above the ground. How fast is the ball travelling when it hits the ground? Use energy concepts.