Concept explainers
A ball is thrown straight upward with an initial velocity of 18 m/s. Use g = 10 m/s2 for computations listed here.
- a. What is its velocity at the high point in its motion?
- b. How much time is required to reach the high point?
- c. How high above its starting point is the ball at its high point?
- d. How high above its starting point is the ball 3 seconds after it is released?
- e. Is the ball moving up or down 2 seconds after it is released?
(a)
The velocity of the ball at the high point.
Answer to Problem 1SP
The velocity of the ball at the high point is
Explanation of Solution
Given Info: A ball is thrown up with initial velocity
The velocity is defined as the rate of change of displacement of the object.
The ball is thrown up. The displacement is upwards but it is acted upon by the acceleration due to gravity which is acting in the downward direction. This means that the velocity decreases as it goes up. This means that velocity becomes zero as the ball is at the highest point. Therefore, the velocity is
Conclusion:
Thus, the velocity of the ball at the high point is
(b)
The time taken by the ball to reach the high point.
Answer to Problem 1SP
The time taken by the ball to reach the high point is
Explanation of Solution
Given Info: A ball is thrown up with initial velocity
Write the expression for the final velocity at the high point.
Here,
Substitute
Substitute
Conclusion:
Thus, the time taken by the ball to reach the high point is
(c)
The height of the ball above its starting point at its high point.
Answer to Problem 1SP
The height of the ball above its starting point at its high point is
Explanation of Solution
Given Info: A ball is thrown up with initial velocity
Write the expression for the vertical distance travelled.
Here,
Substitute
Conclusion:
Thus, the height of the ball above its starting point at its high point is
(d)
The height of the ball above its starting point
Answer to Problem 1SP
The height of the ball above its starting point
Explanation of Solution
Given Info: A ball is thrown up with initial velocity
Write the expression for the vertical distance travelled.
Substitute
Conclusion:
Thus, the height of the ball above its starting point
(e)
Whether the ball is moving up or down
Answer to Problem 1SP
The ball is moving down
Explanation of Solution
Given Info: A ball is thrown up with initial velocity
Write the expression for the final velocity at the high point.
Substitute
Substitute
This is less than
Conclusion:
Thus, the ball is moving down
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Chapter 3 Solutions
Physics of Everyday Phenomena
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