The 2-Mg truck is traveling at 15 m/s when the brakes on all its wheels are applied, causing it to skid for a distance of 10 m before coming to rest. Determine the constant horizontal force developed in the coupling C, and the frictional force developed between the tires of the truck and the road during this time. The total mass of the boat and trailer is 1 Mg.

If the rod of negligible mass is subjected to a couple moment of M=(30 $t^{2}$) N.m, and the engine of the car supplies a traction force of F=(15 t) N to the wheels, where t is in seconds, determine the speed of the car at the instant t=5 s. The car starts from rest. The total mass of the car and rider is 150 kg . Neglect the size of the car.

The 75-kg man pushes on the 150-kg crate with a horizontal force F. If the coefficients of static and kinetic friction between the crate and the surface are $\mu_s = 0.3$ and $\mu_k = 0.2$, and the coefficient of static friction between the man’s shoes and the surface is $\mu_s = 0.8$, show that the man is able to move the crate. What is the greatest acceleration the man can give the crate?

The 0.5-lb ball is guided along the vertical circular path $r = 2r_c \cos \theta$ using the arm OA. If the arm has an angular velocity $\dot{\theta}$= 0.4 rad/s and an angular acceleration $\ddot{\theta} = 0.8$ rad/s$^2$ at the instant $\theta = 30^o$, determine the force of the arm on the ball. Neglect friction and the size of the ball. Set $r_c$= 0.4 ft.

The tractor-trailer unit is moving down the incline with a speed of 5 mi/hr when the driver brakes the tractor to a stop in a distance of 4 ft. Estimate the percent increase n in the hitch-force component which is parallel to the incline, compared with the force present at steady speed. The cart and its load combined weigh 500 lb. State any assumptions.

Which sentence contains an example of personification?

A. The wind whipped through the trees, their new leaves singing a beautiful song to Samantha.

B. The branches and dead leaves crackled under her feet.

C. She imagined being an explorer in the 1600s, before there were trails and markers to guide the way.

D. Samantha could hardly believe her luck to see a bear on the first day.

A model airplane descends in a vertical dive through air at standard conditions ( 1 atmosphere and $20^{\circ} \mathrm{C}$ ). The majority of the drag is due to skin friction on the wing (like that on a flat plate). The wing has a span of $1 \mathrm{~m}$ (tip to tip) and a chord length (leading edge to trailing edge distance) of $10 \mathrm{~cm}$. The leading edge is rough, so the turbulent boundary layer is "tripped." The model weighs $3 \mathrm{~N}$. Find the speed (in meters per second) at which the model will fall.

A model airplane has a wing span of $6\ \mathrm{ft}$ and a chord (leading edge-trailing edge distance) of $4.5 \mathrm{in}$. The model flies in air at $60^{\circ} \mathrm{F}$ and atmospheric pressure. The wing can be regarded as a flat plate so far as drag is concerned. (a) At what speed will a turbulent boundary layer start to develop on the wing? (b) What will be the total drag force on the wing just before turbulence appears?

Suppose that you are driving an 18-wheeler tractor-trailer truck along the highway. A car pulls up alongside your truck and then moves ahead very slowly. As it passes, the combined sound of the car and truck engines pulsates louder and softer. The combined sound can be either a sum of the two sinusoids or a product of them.

At what rate is the car's engine rotating?

When trailing a car on a highway, you are advised to maintain a trailing distance that is often quoted in terms of car lengths, such as in "stay back by 3 car lengths." Suppose the other car suddenly stops (it hits, say, a large stationary truck). Assume a car length $L$ is $4.50 \mathrm{~m}$, your car speed $v_0$ is $31.3 \mathrm{~m} / \mathrm{s}(70 \mathrm{mi} / \mathrm{h})$, your trailing distance is $n L=10.0 L$, and the acceleration magnitude at which your car can brake is $8.50 \mathrm{~m} / \mathrm{s}^2$. What is your speed just before colliding with the other car if (a) your reaction time $t_r$ to start braking is $0.750 \mathrm{~s}$ and (b) automatic braking is immediately started by your car's radar system that continuously monitors the road? What is the minimum value for $n$ needed to avoid a collision with (c) the reaction time $t_r$ and (d) automatic braking?

Consider the following hypothesis test:

$$\begin{array} { l } { H _ { 0 } : \mu \leq 12 } \\ { H _ { \mathrm { a } } : \mu > 12 } \end{array}$$

A sample of 25 provided a sample mean $\overline { x } = 14$ and a sample standard deviation $s = 4.32$.

Compute the value of the test statistic.

Four hundred people were selected from each of the four geographic regions (Midwest, Northeast, South. West) of the United States, and they were asked which form of camping they prefer. Pop-up camper/trailer, family-style (tenting with restrooms), rustic (tenting, no restrooms), or none were the options. The following table displays the survey's findings.

$$\begin{array}{lcccr} \hline & \text { Midwest } & \text { Northeast } & \text { South } & \text { West } \\ \hline \text { Camper/trailer } & 132 & 129 & 129 & 135 \\ \text { Family style } & 180 & 175 & 168 & 146 \\ \text { Rustic } & 46 & 50 & 59 & 68 \\ \text { None } & 42 & 46 & 44 & 51 \\ \hline \end{array}$$

Can you conclude that the distributions of preferred camping types are different for at least two of the regions based on the evidence from these samples? Use $\alpha=.01$.

A random sample of 502 Vail Resorts' guests were asked to rate their satisfaction on various attributes of their visit on a scale of 1-5 with 1= very unsatisfied and 5= very satisfied. The regression model was Y= overall satisfaction score, $X_1$= lift line wait, $X_2$= amount of ski trail grooming, $X_3$= ski patrol visibility, and $X_4$= friendliness of guest services. (a) Calculate the t statistic for each coefficient to test for $\beta_j=0$. (b) Look up the critical value of Student's t in Appendix D for a two-tailed test at $\alpha=.01$. Which coefficients differ significantly from zero? (c) Use Excel to find a p-value for each coefficient.

$$\begin{array}{lcc} \hline \text { Predictor } & \text { Coefficient } & \text { SE } \\ \hline \text { Intercept } & 2.8931 & 0.3680 \\ \text { LiftWait } & 0.1542 & 0.0440 \\ \text { AmountGroomed } & 0.2495 & 0.0529 \\ \text { SkiPatroMisibility } & 0.0539 & 0.0443 \\ \text { FriendlinessHosts } & -0.1196 & 0.0623 \\ \hline \end{array}$$

A model airplane has a wing span of 3.1 ft and a chord (leading edge–trailing edge distance) of 5 in. The model flies in air at 60$^{\circ}F$ and atmospheric pressure. The wing can be regarded as a flat plate so far as drag is concerned. (a) At what speed will a turbulent boundary layer start to develop on the wing? (b) What will be the total drag force on the wing just before turbulence appears?