Lesson: Conservation of Momentum

A firework is tied to a toy car to make a toy rocket car. The firework ejects exhaust from its base. The exhaust has a mass of 15 g and moves away from the firework at a constant speed of 55 m/s. The rocket car has a mass of 75 g. What constant speed does the rocket car move at?

A boy’s yo-yo has a mass of 20 g. The yo-yo runs down its string at a constant speed of 50 mm/s until it reaches the end of the string. When the yo-yo is at the end of the string, the boy jerks the string upward and this motion increases the upward momentum of the yo-yo by 0.0015 kg⋅m/s. At what instantaneous speed, in millimeters per second, does the yo-yo move up its string after the momentum change occurs?

A conveyer belt consists of a surface that is a sheet of material wrapped around continually turning wheels that move the surface at an average speed of 6.25 cm/s, as shown in the diagram. When a bag containing 150 g of shopping is placed on the moving surface, the surface and the shopping both have an average speed of 5 cm/s. What is the mass of the surface in grams?