A 2000 kg car moving east at 10 m/s collides with a 1500 kg car moving north at 12 m/s. If they stick together after collision, what is the direction of their motion relative to east?
Correct: A
Use conservation of momentum in x and y directions. p_x: (2000 kg)(10 m/s) = 20000 kg·m/s east. p_y: (1500 kg)(12 m/s) = 18000 kg·m/s north. Total mass = 3500 kg. v_x = 20000/3500 ≈ 5.71 m/s. v_y = 18000/3500 ≈ 5.14 m/s. θ = tan⁻¹(5.14/5.71) ≈ 43.2°.