91影视

Think of several examples in everyday life of motions that are, at least approximately, simple harmonic. In what respects does each differ from SHM?

A diatomic molecule can be modeled as two point masses, $m_1$and $m_2$, slightly separated (Fig. Q9.2). If the molecule is oriented along the y-axis, it has kinetic energy K when it spins about the x-axis. What will its kinetic energy (in terms of K) be if it spins at the same angular speed about (a) the z-axis and (b) the y-axis?

鈥淚n general, the normal force is not equal to the weight.鈥� Give an example in which these two forces are equal in magnitude, and at least two examples in which they are not.

An elevator is hoisted by its cables at constant speed. Is the total work done on the elevator positive, negative, or zero? Explain.

A rubber hose is attached to a funnel, and the free end is bent around to point upward. When water is poured into the funnel, it rises in the hose to the same level as in the funnel, even though the funnel has a lot more water in it than the hose does. Why? What supports the extra weight of the water in the funnel?

Using a cable with a tension of 1350 N, a tow truck pulls a car 5.00 Km along a horizontal roadway. (a) How much work does the cable do on the car if it pulls horizontally? If it pulls at$\mathbf{35}\mathbf{掳}$above the horizontal? (b) How much work does the cable do on the two trucks in both cases of part (a)? (c) How much work does gravity do on the car in part (a)?

A rhinoceros is at the origin of coordinates at time ${\mathit{t}}_{\mathbf{1}}\mathbf{=}\mathbf{0}$. For the time interval from ${\mathit{t}}_{\mathbf{1}}\mathbf{=}\mathbf{0}$to ${\mathit{t}}_{\mathbf{2}}\mathbf{=}\mathbf{12}\mathbf{.}\mathbf{0}\mathbf{}\mathit{s}$, the rhino鈥檚 average velocity has x-component - 3.8 m/s and y-component 4.9 m/s . At time ${\mathit{t}}_{\mathbf{2}}\mathbf{=}\mathbf{12}\mathbf{}\mathit{s}$,

(a) what are the x and y-coordinates of the rhino?

(b) How far is the rhino from the origin?

The maximum height a typical human can jump from a crouched start is about 60 cm. By how much does the gravitational potential energy increase for a 72 kgperson in such a jump? Where does this energy come from?

In a certain track and field event, the shotput has a mass of 7.30 kg and is released with a speed of $\mathbf{15}\mathbf{.}\mathbf{0}\mathbf{m}\mathbf{/}\mathbf{s}\mathbf{}\mathbf{at}\mathbf{}\mathbf{40}\mathbf{.}\mathbf{0}\mathbf{掳}$above the horizontal over a competitor鈥檚 straight left leg. What are the initial horizontal and vertical components of the momentum of this shotput?

In an experiment, a shearwater (a seabird) was taken from its nest, flown 5150 km away, and released. The bird found its way back to its nest 13.5 days after release. If we place the origin at the nest and extend the +x-axis to the release point, what was the bird鈥檚 average velocity in (a) for the return flight and (b) for the whole episode, from leaving the nest to returning?