In Figure 4-38a, a 0.500-kg block is suspended at the midpoint of a 1.25-m-long string. The ends of the string are attached to the ceiling at points separated by 1.00 m.

$(b)$ What is the tension in the string?

A car rounds an unbanked curve of radius 65 m. If the coefficient of static friction between the road and car is 0.70, what is the maximum speed at which the car traverse the curve without slipping?

A patient has developed an aneurysm in the aorta, a short section where the diameter is twice the normal diameter. In the aneurysm, the speed of the blood is_______ then in the section before the aneurysm, and the pressure is______ then in the section before the aneurysm.
A. Greater, greater
B. Greater, less
C. Less, greater
D. Less, less

A patient has developed a narrowing of the coronary arteries that provide blood to the heart. If the rate of blood flow through the arteries is to stay the same,
A. The length of the arteries must decrease as well.
B. The speed of the flow must not change.
C. The pressure difference across the arteries must stay the same, requiring a decrease in blood pressure.
D. The pressure difference across the arteries must increase, requiring an increase in blood pressure.

If a car takes a banked curve at less than the ideal speed, friction is needed to keep it from sliding toward the inside of the curve (a problem on ice mountain roads). (a) Calculate the ideal speed to take a 100.0 m radius curve banked at 15.0°. (b) What is the minimum coefficient of friction needed for a frightened driver to take the same curve at 20.0 km/h?

(a) What is the radius of a bobsled turn banked at 75.0° and taken at 30.0 m/s, assuming it is ideally banked? (b) Calculate the centripetal acceleration. (c) Does this acceleration seem large to you?

The blood pressure at your heart is approximately 100 mm Hg. As blood is pumped from the left ventricle of your heart, it flows through the aorta, a single large vessel with a diameter of about 2.5 cm. The speed of blood flow in the aorta is about 60 cm/s. Any change in pressure as blood flows in the aorta is due to the change in height: the vessel is large enough that viscous drag is not a major factor into successively smaller and smaller blood vessels until it reaches the capillaries. Blood flows in the capillaries at the much lower speed of approximately 0.7 mm/s. The diameter of capillaries and other small blood vessels is so small that viscous drag is a major factor. Suppose that in response to some stimulus a small blood vessel narrows to 90% of its original diameter. If there is no change in the pressure across the vessel, what is the ratio of the new volume flow rate to the original flow rate? A. 0.66 B. 0.73 C. 0.81 D. 0.90

A 15-m-long garden hose has an inner diameter of 2.5 cm. One end is connected to a spigot; $20 ^ { \circ } \mathrm { C }$ water flows from the other end at a rate of 1.2 L/s. What is the gauge pressure at the spigot end of the hose? A. 1900 Pa B. 2700 Pa C. 4200 Pa D. 5800 Pa E. 7300 Pa

A $55 \mathrm{~g}$ soapstone cube-a whisky stone-is used to chill a glass of whisky. Soapstone has a density of $3000 \mathrm{~kg} / \mathrm{m}^3$, whisky a density of $940 \mathrm{~kg} / \mathrm{m}^3$. What is the approximate normal force of the bottom of the glass on a single stone?
A. $0.1 \mathrm{~N}$
B. $0.2 \mathrm{~N}$
C. $0.3 \mathrm{~N}$
D. $0.4 \mathrm{~N}$

What is the ideal banking angle for a gentle turn of 1.20-km radius on a highway with a 105 km/h speed limit (about 65 mi/h), assuming everyone travels at the limit?

A contestant in a winter sporting event pushes a $45.0-\mathrm{kg}$ block of ice across a frozen lake as shown in given figure. (a) Calculate the minimum force $F$ he must exert to get the block moving. (b) What is the magnitude of its acceleration once it starts to move, if that force is maintained?

A contestant in a winter sporting event pushes a 45.0-kg block of ice across a frozen lake as shown below. (a) Calculate the minimum force $F$ he must exert to get the block moving. (b) What is its acceleration once it starts to move, if that force is maintained?

A machine at a post office sends packages out a chute and down a ramp to be loaded into delivery vehicles. (a) Calculate the acceleration of a box heading down a 10.0° slope, assuming the coefficient of friction for a parcel on waxed wood is 0.100. (b) Find the angle of the slope down which this box could move at a constant velocity. You can neglect air resistance in both parts.

Consider the 65.0-kg ice skater being pushed by two others shown in given figure. (a) Find the direction and magnitude of $\mathbf{F}_{\text {tot }}$, the total force exerted on her by the others, given that the magnitudes $F_1$ and $F_2$ are $26.4 \mathrm{~N}$ and $18.6 \mathrm{~N}$, respectively. (b) What is her initial acceleration if she is initially stationary and wearing steel-bladed skates that point in the direction of $\mathbf{F}_{\text {tot }}$ ? (c) What is her acceleration assuming she is already moving in the direction of $\mathbf{F}_{\text {tot }}$ ? (Remember that friction always acts in the direction opposite that of motion or attempted motion between surfaces in contact.)