A pinball machine launches a 139 g ball

with a spring-driven plunger. The game
board is inclined at 8 ◦
above the horizontal.
Assume: The plunger’s mass and frictional
effects are negligible. The acceleration of
gravity is 9.8 m/s2
Find the force constant k of the spring that
will give the ball a speed of 123 cm/s when the
plunger is released from rest with the spring
compressed 5 cm from its relaxed position.
Answer in units of N/m.