JEE Main Physics question
A spring gun of spring constant 90 N cm⁻¹ is compressed 12 cm by a ball of mass 16 g. If the trigger is pulled, the velocity of the ball is [Kerala CEE 2008]
Answer: (D)
Solution
k = 90 N/cm = 9000 N/m. Spring PE = ½kx² = ½(9000)(0.12)² = 64.8 J, all converted to KE: ½(0.016)v² = 64.8 ⟹ v² = 8100 ⟹ v = 90 ms⁻¹.