Playing in the street, a child accidentally tosses a ball (mass m) with a speed
ID: 1600520 • Letter: P
Question
Playing in the street, a child accidentally tosses a ball (mass m) with a speed of v = 17 m/s toward the front of a car (mass M) that is moving directly toward him with a speed of = 17 m/s. Treat this collision as a 1-dimensional elastic collision. After the collision, the ball is moving with speed v' back toward the child and the car is moving with speed V' in its original direction. When we combine the equation from Part A with the conservation of momentum equation, we can solve for both final speeds. This relationship will involve the masses of the ball and the car. but we can apply a simplifying assumption: the car is so massive compared with the ball that its speed will not change at all as a result of this collision. Translate this sentence into an equation, what is V' equal to? Now, having made this assumption, it becomes possible to solve the equation from Part A for the final speed of the ball, what is it? Express your answer using two significant figures.Explanation / Answer
(B). V ' = V = -17 m/s negative sign indicates that the car moves opposite to the direction of ball.
This is perfectly eleastic,
So, coefficient of restitution = 1
relative velocity after collision / reletive velocity before collision = 1
(V ' - v ' ) / ( v - V ) = 1
V ' - v ' = v - V
V - v ' = v - V
v ' = V + V - v
= 2V - v
= 2(-17) - 17
= -34 -17
= -51 m/s