Kinematics: Constant Acceleration & Projectiles

Worked: stopping, then throwing

A car at 60 mph brakes at a steady 15 ft/s². Convert first: 60 × 1.467 = 88 ft/s. No time is asked, so use v² = v₀² + 2as: 0 = 88² − 2 × 15 × s, giving s = 7,744/30 = 258 ft. If the time is wanted as well, t = 88/15 = 5.87 s.

A stone is thrown at 40 ft/s, 30° above level ground. The vertical component is 20 ft/s, so it is airborne 2 × 20/32.2 = 1.24 s. The horizontal component is 34.6 ft/s, so it lands 34.6 × 1.24 = 43.0 ft away.