Concept explainers
(a)
Give estimation on weight and area of a typical car.
(a)
Answer to Problem 40PQ
A typical car can have weight around
Explanation of Solution
The average of weight of car can be taken as two thousand pounds. Express two thousand pounds in kilogram.
Normally a car can have
Conclusion:
Therefore, a typical car can have weight around
(b)
Draw the graph of
(b)
Answer to Problem 40PQ
Graph of
Explanation of Solution
The graph of
Write the equation for drag force.
Here,
Substitute
The equation tells that the drag force is varying with the square of speed of car. It can be seen that the graph is also conveying the same result. Graph shows that
Conclusion:
Therefore, the graph of
(c)
The value of Rolling
(c)
Answer to Problem 40PQ
Rolling frictional force is
Explanation of Solution
Write the equation to find the rolling friction.
Here,
Conclusion:
Substitute
It can be seen that
Therefore, the rolling frictional force is
(d)
The speed at which drag force equals rolling frictional force and the range of speed which the drag force can be neglected.
(d)
Answer to Problem 40PQ
The speed at which drag force equals rolling frictional force is
Explanation of Solution
Equate the right hand sides of equations (1) and (II).
Rewrite the above expression in terms of
It can be seen that lower speeds, drag force will be lesser than rolling frictional force. So drag force can be neglected at lower speed. It is better to limit the speed within
Conclusion:
Therefore, the speed at which drag force equals rolling frictional force is
(e)
The change in answer on the assumption that
(e)
Answer to Problem 40PQ
Explanation of Solution
Therefore, the
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Chapter 6 Solutions
Physics for Scientists and Engineers: Foundations and Connections
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