physics!

posted by .

Playing in the street, a child accidentally tosses a ball at 21 m/s toward the front of a car moving toward him at 18 m/s. What is the ball's speed after it rebounds elastically from the car?

  • physics! -

    In an elastic collision (1/2) m v^2 does not change.
    21 m/s

  • physics! -

    in the frame of the car, the ball comes in with 39 m/s speed, and bounces back at 39 m/s in the other direction. In the observer frame we need to add the 18 m/s relative speed of the car, and get 57 m/s

  • physics! -

    57m/s

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. college physics

    A small ball of mass m is aligned above a larger ball of mass M = 0.79 kg (with a slight separation), and the two are dropped simultaneously from height h = 2.0 m. (Assume the radius of each ball is negligible relative to h). (a) If …
  2. physics

    A train is moving with a speed of 50 miles per hour. A man standing in the rear of a train car throws a ball toward the front of the train with a speed of 10 miles per hour. If a stationary observer outside the train sees this happen, …
  3. Physics

    A tennis ball with a speed of 14m/s is moving perpendicular to a wall. After striking the wall, the ball rebounds in the opposite direction with a speed of 11.41m/s. If the ball is in contact with the wall for 0.0112s, what is the …
  4. physics

    A tennis ball with a speed of 12.5 m/s is moving perpendicular to a wall. After striking the wall, the ball rebounds in the opposite direction with a speed of 11.4 m/s. If the ball is in contact with the wall for 0.0139 s, what is …
  5. physics

    A soccer player kicks the ball toward a goal that is 15.0 m in front of him. The ball leaves his foot at a speed of 17.1 m/s and an angle of 35.0 ° above the ground. Find the speed of the ball when the goalie catches it in front of …
  6. physics

    A soccer player kicks the ball toward a goal that is 15.0 m in front of him. The ball leaves his foot at a speed of 17.1 m/s and an angle of 35.0 ° above the ground. Find the speed of the ball when the goalie catches it in front of …
  7. physics

    a car is moving foward at 15.7m/s. a person in the bus throws a ball horizontally toward the front of the car at 17.5 m/s from your perspective as an observer outside the car the tennis ball appears to moving at what velocity?
  8. Physics

    A soccer player kicks the ball toward a goal that is 23.0 m in front of him. The ball leaves his foot at a speed of 17.6 m/s and an angle of 29.0 ° above the ground. Find the speed of the ball when the goalie catches it in front of …
  9. physics

    A train is moving with a speed of 50 miles per hour. A man standing in the rear of a train car throws a ball toward the front of the train with a speed of 10 miles per hour. If a stationary observer outside the train sees this happen, …
  10. Physics

    15)A small ball of mass m is aligned above a larger ball of mass M = 1.2 kg (with a slight separation, as with the baseball and basketball of Figure (a)), and the two are dropped simultaneously from height h = 2.4 m. (Assume the radius …

More Similar Questions