Based on the information in Table 5.1, estimate
a. The weight of a laptop computer.
b. The propulsion force of a bicycle.
Weight of an object is defined as the force due to its mass and the acceleration due to gravity.
The computer has its mass as well as the acceleration due to gravity.
The formula to calculate the weight is given by
The value of mass of computer is 5 lb.
Therefore, the weight would be 5lbf. (Here 1 lbf is taken as 5N)
According to the table 5.1, the weight is 25 N.
Since the given involves error which is large in value, we considerably take the value 1 lbf is approximated to 4.45 N.
Therefor the weight of typical laptop is 22.25 N.
The force is defined as the product of its mass and acceleration.
The propulsion force is not due to the bicycle but due to the rider 's force that allows the bicycle to move.
Consider the mass of the rider and the bicycle is 100 kg.
Consider the acceleration of the bicycle be 0.2 m/s2.
Then the propulsion force is calculated as:
Therefore, the propulsion force of a bicycle is 50 N.
Problems 35 through 40 show a free-body diagram. For each:
a. Identify the direction of the acceleration vector and show it as a vector next to your diagram. Or, if appropriate, writeb. If possible, identify the direction of the velocity vector and show it as a labeled vector.
c. Write a short description of a real object for which this is the
correct free-body diagram. Use Examples 5.4, 5.5, and 5.6 as
models of what a description should be like.
A rubber ball bounces. We’d like to understand how the ball bounces. a. A rubber ball has been dropped and is bouncing off the floor. Draw a motion diagram of the ball during the brief time interval that it is in contact with the floor. Show 4 or 5 frames as the ball compresses, then another 4 or 5 frames as it expands. What is the direction of a u during each of these parts of the motion? b. Draw a picture of the ball in contact with the floor and identify all forces acting on the ball. c. Draw a free-body diagram of the ball during its contact with the ground. Is there a net force acting on the ball? If so, in which direction? d. Write a paragraph in which you describe what you learned from parts a to c and in which you answer the question: How does a ball bounce?
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