A Perfectly Inelastic Collision?

📌 CONCEPT: A perfectly inelastic collision is a type of collision where the colliding objects stick together after the collision, resulting in a single object with a combined mass and velocity.

📐 RULE / FORMULA: We use the law of conservation of momentum to solve this problem. The formula for conservation of momentum is m1u1 + m2u2 = (m1 + m2)v, where m1 and m2 are the masses of the objects, u1 and u2 are their initial velocities, and v is the final velocity of the combined object.

💡 WORKED EXAMPLE: Given m1 = 3 kg, m2 = 2 kg, u1 = 25 m/s, and u2 = -10 m/s, we can calculate the final velocity v using the formula: 3(25) + 2(-10) = (3 + 2)v, 75 - 20 = 5v, 55 = 5v, v = 11 m/s.

⚠️ COMMON MISTAKE: Students often forget to consider the direction of the velocities in the formula, leading to incorrect results. They should ensure that the velocities are added or subtracted according to their direction.