Irina Lyublinskaya, Gregg Wolfe, Douglas Ingram , Liza Pujji
ISBN #9781938168932
2,282 Questions
Homework Questions
This chapter emphasizes the fundamental role of forces in dynamics, illustrating how Newton’s three laws provide the framework for analyzing motion. Key concepts include the vector nature of force, the importance of net external forces as depicted in free?body diagrams, and how friction, drag, and elasticity impact real-world systems. A deep understanding of these concepts allows us to quantitatively solve problems by resolving forces into components and applying F = ma, as well as appreciate the universal presence of action–reaction pairs in all interactions.
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A 63.0 -kg sprinter starts a race with an acceleration of4.20 $\mathrm{m} / \mathrm{s}^{2} .$ What is the net external force on him?
If the sprinter from the previous problem accelerates at that rate for 20 m, and then maintains that velocity for the remainder of the 100-m dash, what will be his time for the race?
A cleaner pushes a 4.50-kg laundry cart in such a way that the net external force on it is 60.0 N. Calculate the magnitude of its acceleration.
Since astronauts in orbit are apparently weightless, a clever method of measuring their masses is needed to monitor their mass gains or losses to adjust diets. One way to do this is to exert a known force on an astronaut and measure the acceleration produced. Suppose a net external force of 50.0 N is exerted and the astronaut’s acceleration is measured to be 0.893 $\mathrm{m} / \mathrm{s}^{2}$ . (a) Calculate her mass. (b) By exerting a force on the astronaut, the vehicle in which they orbit experiences an equal and opposite force. Discuss how this would affect the measurement of the astronaut’s acceleration. Propose a method in which recoil of the vehicle is avoided.
In Figure 4.7 , the net external force on the 24 -kg mower is stated to be 51 N. If the force of friction opposing the motion is $24 \mathrm{N},$ what force $F$ (in newtons) is the person exerting on the mower? Suppose the mower is moving at 1.5 $\mathrm{m} / \mathrm{s}$ when the force $F$ is removed. How far will the mower go before stopping?