A 97-kg sprinter wishes to accelerate from rest to a speed of 13 m/s in a distance of 22 m. What coefficient of static friction is required between the sprinter's shoes and the track?

Coffee To Go A person places a cup of coffee on the roof of her car while she dashes back into the house for a forgotten item. When she returns to the car, she hops in and takes off with the coffee cup still on the roof. What is the smallest amount of time in which the person can accelerate the car from rest to $15 \mathrm{~m} / \mathrm{s}$ and still keep the coffee cup on the roof?

a. What happens when an electric current is produced? b. Contrast electric current and static electricity. c. Explain why electric current cannot exist if an electric circuit is broken.

A $90^{\circ}$ elbow in a horizontal pipe is used to direct water flow upward at a rate of $30 \mathrm{~kg} / \mathrm{s}$. The diameter of the entire elbow is $10 \mathrm{~cm}$. The elbow discharges water into the atmosphere, and thus the pressure at the exit is the local atmospheric pressure. The elevation difference between the centers of the exit and the inlet of the elbow is $40 \mathrm{~cm}$. In this case an another (identical) elbow attached to the existing elbow so that the fluid makes a U-turn. The weight of the elbow and the water in it is considered to be negligible. Calculate $(a)$ the gage pressure at the center of the inlet of the elbow and $(b)$ the anchoring force needed to hold the elbow in place. Take the momentum-flux correction factor to be $1.03$ at both the inlet and the outlet.

With this type of binding, the Java Virtual Machine determines at runtime which

method to call, depending on the type of the object that a variable references.

a. static

b. early

c. flexible

d. dynamic

The table displays how many of each letter are in a bag. Find the odds in favor of C.

$$\begin{array}{|c|c|} \hline \text { Letter } & \begin{array}{c} \text { How Many } \\ \text { in Bag } \end{array} \\ \hline \text { A } & 5 \\ \hline \text { B } & 4 \\ \hline \text { C } & 6 \\ \hline \text { D } & 2 \\ \hline \text { E } & 8 \\ \hline \end{array}$$

You push a box along the floor against a constant force of friction. When you push with a horizontal force of 75 N, the acceleration of the box is 0.50 m/s$^{2}$; when you increase the force to 81 N, the acceleration is 0.75 m/s$^{2}$. Find (a) the mass of the box and (b) the coefficient of kinetic friction between the box and the floor.

Indicate the statement as true or false The undamped natural frequency of a system is denoted as $\sqrt{g / \delta_{\mathrm{st}}}$, where $\delta_{\mathrm{st}}$ is the static deflection of the mass.

Blake Knudson owns and operates Grab Bag Delivery Services. On January 1, 2013, Retained Earnings had a balance of $918,000. During the year, no additional capital stock was issued and$15,000 of dividends were paid. For the year ended December 31, 2013, Grab Bag Delivery Services reported a net loss of $43,500. Prepare a retained earnings statement for the year ended December 31, 2013.

A worker pushes horizontally on a $35 \mathrm{~kg}$ crate with a force of magnitude $110 \mathrm{~N}$. The coefficient of static friction between the crate and the floor is $0.37$. Does the crate move?

Wilbur is asking Mr. Ed the talking horse to pull a cart. Mr. Ed replies that he would like to, but the laws of nature just won't allow it. According to Newton's third law, he says, if he pulls on the cart, it pulls back on him with an equal force. Clearly, then, the net force is zero, and the cart will stay put. How should Wilbur answer the clever horse?

What is the minimum horizontal force $F$ needed to make the box start moving in the given figure? The coefficients of kinetic and static friction between the box and the floor are $0.24$ and $0.41$, respectively.

What is the minimum horizontal force $F$ needed to make the box start moving in the given figure? The coefficients of kinetic and static friction between the box and the floor are $0.27$ and $0.38$, respectively.

A $90^\circ$ elbow in a horizontal pipe is used to direct water flow upward at a rate of 40 kg/s. The diameter of the entire elbow is 10 cm. The elbow discharges water into the atmosphere, and thus the pressure at the exit is the local atmospheric pressure. The elevation difference between the centers of the exit and the inlet of the elbow is 50 cm. The weight of the elbow and the water in it is considered to be negligible. Determine (a) the gage pressure at the center of the inlet of the elbow and (b) the anchoring force needed to hold the elbow in place. Take the momentum-flux correction factor to be 1.03 at both the inlet and the outlet.