A 30 kg box with a height of 0.230 meters is on top of a 0.5-meter-high table and is initially at rest. A 5kg projectile having a speed of 20 m/s was launched at the horizontal ground, 6.972 meters (horizontal distance) away from the nearest vertical wall of the box. When the projectile hit the vertical side of the box, it rebound at a speed of -11.143 m/s and the box developed a speed of 5.140 m/s. At what angle was the projectile launched?

A 30 kg box with a height of 0.230 meters is on top of a 0.5-meter-high table and is initially at rest. A 5kg projectile having a speed of 20 m/s was launched at the horizontal ground, 6.972 meters (horizontal distance) away from the nearest vertical wall of the box. When the projectile hit the vertical side of the box, it rebound at a speed of -11.143 m/s and the box developed a speed of 5.140 m/s. At what angle was the projectile launched?