Question

A 2.5 kg block is launched along the ground by a spring with a spring constant of 56 N/m. The spring is initially compressed 0.75 m.

Disregarding friction, how fast will the block move after the spring is released all the way and the block slides away from it?

3.5 m/s
4.1 m/s
13 m/s
16 m/s

Answer 1

Use energy conservation: (1/2)kx^2 = (1/2)mv^2. So v = sqrt(kx^2/m).

Compute: kx^2 = 56*(0.75)^2 = 56*0.5625 = 31.5, so v = sqrt(31.5/2.5) = sqrt(12.6) ≈ 3.55 m/s.

Answer: 3.5 m/s.