91影视

During an Olympic bobsled run, the Jamaican team makes a turn of radius ${}^{\mathbf{7}\mathbf{.}\mathbf{6}\mathbf{}\mathbf{m}}$at a speed of ${}^{\mathbf{96}\mathbf{.}\mathbf{6}\mathbf{}\mathbf{km}\mathbf{/}\mathbf{h}}$. What is their acceleration in terms of${}^{\mathbf{g}}$?

A student of weight${}^{\mathbf{667}\mathbf{}\mathbf{N}}$rides a steadily rotating Ferris wheel (the student sits upright). At the highest point, the magnitude of the normal forceon the student from the seat is${}^{\mathbf{556}\mathbf{}\mathbf{N}}$. (a) Does the student feel 鈥渓ight鈥� or 鈥渉eavy鈥� there? (b) What is the magnitude of at the lowest point? If the wheel鈥檚 speed is doubled, what is the magnitude${}^{{\mathbf{F}}_{\mathbf{N}}}$at the (c) highest and (d) lowest point?

A police officer in hot pursuit drives her car through a circular turn of radius ${}^{\mathbf{300}\mathbf{}\mathbf{m}}$with a constant speed of ${}^{\mathbf{80}\mathbf{.}\mathbf{0}\mathbf{}\mathbf{km}\mathbf{/}\mathbf{h}}$. Her mass is${}^{\mathbf{55}\mathbf{.}\mathbf{0}\mathbf{kg}}$. What are (a) the magnitude and (b) the angle (relative to vertical) of the net force of the officer on the car seat? (Hint: Consider both horizontal and vertical forces)

A circular-motion addict of mass${}^{\mathbf{80}\mathbf{k}\mathbf{g}}$rides a Ferris wheel around in a vertical circle of radius${}^{\mathbf{10}\mathbf{}\mathbf{m}}$at a constant speed of${}^{\mathbf{6}\mathbf{.}\mathbf{1}\mathbf{}\mathbf{m}\mathbf{/}\mathbf{s}}$. (a) What is the period of the motion? What is the magnitude of the normal force on the addict from the seat when both go through (b) the highest point of the circular path and (c) the lowest point?

A roller-coaster car at an amusement park has a mass of${}^{\mathbf{1200}\mathbf{kg}}$when fully loaded with passengers. As the car passes over the top of a circular hill of radius${}^{\mathbf{18}\mathbf{}\mathbf{m}}$, assume that its speed is not changing. At the top of the hill, what are the (a) magnitude${}^{{\mathbf{F}}_{\mathbf{N}}}$and (b) direction (up or down) of the normal force on the car from the track if the car鈥檚 speed is${}^{\mathbf{V}\mathbf{=}\mathbf{11}\mathbf{}\mathbf{m}\mathbf{/}\mathbf{s}}$? What are (c)${}^{{\mathbf{F}}_{\mathbf{N}}}$and (d) the direction if${}^{\mathbf{V}\mathbf{=}\mathbf{14}\mathbf{}\mathbf{m}\mathbf{/}\mathbf{s}}$?

In Fig. 6-39, a car is driven at constant speed over a circular hill and then into a circular valley with the same radius. At the top of the hill, the normal force on the driver from the car seat is 0. The driver鈥檚 mass is ${}^{\mathbf{70}\mathbf{.}\mathbf{0}\mathbf{}\mathbf{kg}}$.What is the magnitude of the normal force on the driver from the seat when the car passes through the bottom of the valley?

A slide-loving pig slides down a certain${\mathbf{35}}^{\mathbf{鈭�}}$slide in twice the time it would take to slide down a frictionless${\mathbf{35}}^{\mathbf{鈭�}}$slide.What is the coefficient of kinetic friction between the pig and the slide?

In three experiments, three different horizontal forces are applied to the same block lying on the same countertop. The force magnitudes are${\mathit{F}}_{\mathbf{1}}\mathbf{=}\mathbf{12}\mathbf{N}$,${\mathit{F}}_{\mathbf{2}}\mathbf{=}\mathbf{8}\mathbf{N}$, ${\mathit{F}}_{\mathbf{3}}\mathbf{=}\mathbf{4}\mathbf{N}$. In each experiment, the block remains stationary in spite of the applied force. Rank the forces according to (a) the magnitude of the static frictional force on the block from the countertop and (b) the maximum value role="math" localid="1660904123305" ${\mathit{f}}_{\mathbf{s}\mathbf{,}\mathbf{max}}$of that force, greatest first.

An${}^{\mathbf{85}\mathbf{.}\mathbf{0}\mathbf{kg}}$passenger is made to move along a circular path of radius${}^{\mathbf{r}\mathbf{=}\mathbf{3}\mathbf{.}\mathbf{50}\mathbf{}\mathbf{m}}$in uniform circular motion. (a) Figure 6-40a is a plot of the required magnitude${}^{\mathbf{F}}$of the net centripetal force for a range of possible values of the passenger鈥檚 speed v. What is the plot鈥檚 slope at${}^{\mathbf{V}\mathbf{=}\mathbf{8}\mathbf{.}\mathbf{30}\mathbf{}\mathbf{m}\mathbf{/}\mathbf{s}}$? (b) Figure 6-40b is a plot of F for a range of possible values of${}^{\mathbf{T}}$, the period of the motion. What is the plot鈥檚 slope atrole="math" localid="1654172716493" ${}^{\mathbf{T}\mathbf{=}\mathbf{2}\mathbf{.}\mathbf{50}\mathbf{}\mathbf{s}}$?

An airplane is flying in a horizontal circle at a speed of $\mathbf{480}\mathbf{}\mathbf{km}\mathbf{/}\mathbf{h}$(Fig. 6-41). If its wings are tilted at angle$\mathbf{胃}\mathbf{=}\mathbf{}\mathbf{40}\mathbf{掳}$to the horizontal, what is the radius of the circle in which the plane is flying? Assume that the required force is provided entirely by an 鈥渁erodynamic lift鈥� that is perpendicular to the wing surface.