Concept explainers
Two balls are released simultaneously from the top of a tall building. Ball A is simply dropped with no initial velocity, and ball B is thrown downward with an initial velocity of 15 m/s.
- a. What are the velocities of the two balls 1.3 seconds after they are released?
- b. How far has each ball dropped in 1.3 seconds?
- c. Does the difference in the velocities of the two balls change at any time after their release? Explain.
(a)
The velocities of the two balls
Answer to Problem 2SP
The velocities of the two balls A and B
Explanation of Solution
Given Info: A ball is thrown downward with initial velocity
Write the expression for the final velocity.
Here,
For the ball with the initial velocity, substitute
For the ball starting from rest, substitute
Conclusion:
Thus, the velocities of the two balls A and B
(b)
The distance each ball has dropped in
Answer to Problem 2SP
The distance each ball A and B has dropped in
Explanation of Solution
Given Info: A ball is thrown downward with initial velocity
Write the expression for the distance travelled.
Here,
For the ball with the initial velocity, substitute
For the ball starting from rest, substitute
Conclusion:
Thus, the distance each ball A and B has dropped in
(c)
Whether the difference in the velocities of the two balls change at any time.
Answer to Problem 2SP
The difference in the velocities of the two balls does not change at any time as it is given by the initial velocity of the balls.
Explanation of Solution
Write the expression for the final velocity.
This equation gives the final velocity of the balls. The difference in the velocity is given by the initial velocity as the change is usually the acceleration due to gravity multiplied by the time which is the same for both the balls. Thus the difference is only in the initial velocity of the ball which is also a constant value and therefore, does not change at any time.
Conclusion:
Thus, the difference in the velocities of the two balls does not change at any time as it is given by the initial velocity of the balls.
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Chapter 3 Solutions
PHYSICS OF EVERYDAY PHEN (LL)
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