A ball rolling rapidly along a tabletop rolls off the edge and falls tothe floor

Question

A ball rolling rapidly along a tabletop rolls off the edge and falls tothe floor. At the exact instant that the first ball rolls off the edge, a second ball is dropped from the same height. Which ball, if either, reaches the floor first? Explain. The rolling ball reaches the floor first because it has an intial velocity and dropped ball doesnot. The dropped ball reaches the floor first because its velocity is only in the y-direction. Both balls reach the floor at the same time because they both have the same intial zero y-component of velocity. A ball is thrown straight upward. At the very top of its flight, the velocity of the ball is zero. Is its acceleration at this point also zero? Explain. Yes, acceleration is zero because the velocity is also zero. Yes, the acceleration is zero because the ball is thrown straight upward. No, the acceleration due to gravity is constant even at the top of its flight. No, the acceleration is decreasing but will not be zero until the ball lands on the ground. A cannonball fired at an angle of 70 degree to the horizontal stays in the air longer than one fired at 45 degree from the same cannon. will the 70 degree shot travel a greater horizontal distance than the 45 degree shot? Explain. Yes, since the cannonball fired at an angle of 70 degree stays in the air longer it will travel a greater horizontal distance than the cannonball fired at 45 degree. no, the cannonball fired at 70 degree has a larger vertical component of velocity so will have a higher ascent and will not travel as far horizontally as the cannonball fired at 45 degree. There is not enough information to determine which cannnonball will travel a greater horizontal distance. In the diagram, two different trajectories are shown for a ball thrown by a center fielder to home plate in a baseball game. Which of the two trajectories(if either), the higher one or the lower one, will result in a longer time for the ball to reach home plate? Explain. The higher trajectory will result in a longer time because its initial vertical velocity component is larger. The lower trajectory will result in a longer time because its vertical velocity component is smaller. Both trajectories will result in the same amount of time because the horizontal distance transversed is the same.

Explanation / Answer

1. both reach at the same time. because they have same zero y- component velocity and are under the influence of same acceleration, which is accn due to gravity 2. c. no. acceleration due to gravity is constant and non zero 3. b. No. the range is maximum for a ball fired at 45 degrees 4. a. higher trajectory takes longer as its initial vertical velocity is higher.

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