4. A 555-g squirrel with a surface area of 865 cm^2 falls from a 4.4-m tree to the ground. Estimate its terminal velocity. (Use the drag coefficient for a horizontal skydiver. Assume that the cross-sectional area of the squirrel can be approximated as a rectangle of width 11.1 cm and length 22.2 cm. Note, the squirrel may not reach terminal velocity by the time it hits the ground. A. Give the squirrel's terminal velocity, not it's velocity as it hits the ground.) B. What will be the velocity of a 55.5-kg person hitting the ground, assuming no drag contribution in such a short distance?
5. Stokes' law describes sedimentation of particles in liquids and can be used to measure viscosity. Particles in liquids achieve terminal velocity quickly. One can measure the time it takes for a particle to fall a certain distance and then use Stokes' law to calculate the viscosity of the liquid. Suppose a steel ball bearing (density 7.8 ? 10^3 kg/m^3, diameter 2.8 mm) is dropped in a container of motor oil. It takes 10 s to fall a distance of 0.50 m. Calculate the viscosity of the oil.
6. During a circus act, one performer swings upside down hanging from a trapeze holding another, also upside-down, performer by the legs. If the upward force on the lower performer is three times her weight, how much do the bones (the femurs) in her upper legs stretch? You may assume each is equivalent to a uniform rod 31.0 cm long and 1.78 cm in radius. Her mass is 57.5 kg.
7. Calculate the force a piano tuner applies to stretch a steel piano wire 7.00 mm, if the wire is originally 0.850 mm in diameter and 1.30 m long.
8. A disk between vertebrae in the spine is subjected to a shearing force of 530 N. Find its shear deformation taking it to have the shear modulus of 1 ? 10^9 N/m^2. The disk is equivalent to a solid cylinder 0.700 cm high and 4.00 cm in diameter.
9. A moonshiner makes the error of filling a glass jar to the brim and capping it tightly. The moonshine expands more than the glass when it warms up, in such a way that the volume increases by 0.2% (that is, ΔV/V0 = 2 ? 10^-3) relative to the space available. Calculate the force exerted by the moonshine per square centimeter if the bulk modulus is 1.7 ? 10^9 N/m^2, assuming the jar does not break.
10. The three diagrams below show a block of mass m being pulled or pushed at constant acceleration ax along a table with a force P. The coefficient of kinetic friction is μk. What is the friction force in each case? Give your answer in terms of the pushing force P, ax, m, and the angle θ.
https://s.yimg.com/hd/answers/i/899588bb6fb44a11adb56c27f664af7d_A.jpeg?a=answers&mr=0&x=1444003243&s=acaa7308a13b7f6c4ce9d9991b953182
Case (i) fk =
Case (ii) fk=
Case (iii) fk=