Chapter 6: Problem 2
If the scalar product of two nonzero vectors is zero, what can you conclude about their relative directions?
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Chapter 6: Problem 2
If the scalar product of two nonzero vectors is zero, what can you conclude about their relative directions?
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E. coli bacteria swim by means of flagella that rotate about 100 so times per second. A typical \(E .\) coli bacterium swims at \(22 \mu \mathrm{m} / \mathrm{s}\) its flagella exerting a force of \(0.57 \mathrm{pN}\) to overcome the resistance due to its liquid environment. (a) What's the bacterium's power output? (b) How much work would it do in traversing the \(25-\mathrm{mm}\) width of a microscope slide?
Uncompressed, the spring for an automobile suspension is \(45 \mathrm{cm}\) long. It needs to be fitted into a space 32 cm long. If the spring constant is \(3.8 \mathrm{kN} / \mathrm{m},\) how much work does a mechanic have to do to fit the spring?
A truck is moving northward at \(55 \mathrm{mi} / \mathrm{h}\). Later, it's moving eastward at the same speed. Has its kinetic energy changed? Has work been done on the truck? Has a force acted on the truck? Explain.
A force given by \(F=b / \sqrt{x}\) acts in the \(x\) -direction, where \(b\) is a constant with the units \(\mathrm{N} \cdot \mathrm{m}^{1 / 2} .\) Show that even though the force becomes arbitrarily large as \(x\) approaches zero, the work done in moving from \(x_{1}\) to \(x_{2}\) remains finite even as \(x_{1}\) approaches zero. Find an expression for that work in the limit \(x_{1} \rightarrow 0\).
Does your car's kinetic energy change if you drive at constant speed for 1 hour?
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