Biomechanical research has shown that when a 67-kg person is running, the force exerted on each foot as it strikes the ground can be as great as $2300 \mathrm{~N}$. If the only forces acting on the person are (i) the force exerted by the ground and (ii) the person's weight, what are the magnitude and direction of the person's acceleration?

Suppose a rocket launches with an acceleration of $30.5 \mathrm{~m} / \mathrm{s}^2$. What is the apparent weight of an $92-\mathrm{kg}$ astronaut aboard this rocket?

A 65-kg skier speeds down a trail, as shown in Figure . The surface is smooth and inclined at an angle of $22^{\circ}$ with the horizontal. Determine the normal force acting on the skier.

To give a 19-kg child a ride, two teenagers pull on a 3.7-kg sled with ropes. Both teenagers pull with a force of 55 N at an angle of $35^{\circ}$ relative to the forward direction, which is the direction of motion. In addition, the snow exerts a retarding force on the sled that points opposite to the direction of motion and has a magnitude of 57 N. Find the acceleration of the sled and child.

Find the normal force exerted on a 2.9-kg book resting on a surface inclined at $36^{\circ}$ above the horizontal.

A 51.5-kg swimmer with an initial speed of $1.25 \mathrm{~m} / \mathrm{s}$ decides to coast until she comes to rest. If she slows with constant acceleration and stops after coasting $2.20 \mathrm{~m}$, what was the force exerted on her by the water?

A gardener mows a lawn with an old-fashioned push mower. The handle of the mower makes an angle of $35^{\circ}$ with the surface of the lawn. If a $219-\mathrm{N}$ force is applied along the handle of the 19-kg mower, what is the normal force exerted by the lawn on the mower?

As figure shows the normal force as a function of the angle $\theta$ for the suitcase shown in Figure 5-13. Determine the magnitude of the force $\overrightarrow{\mathbf{F}}$ for each of the three curves shown in Figure 5-29. Give your answer in terms of the weight of the suitcase, mg.

Driving home from school one day, you spot a ball rolling out into the street. You brake for 1.20 s, slowing your 950-kg car from 16.0 m/s to 9.50 m/s. (a) What was the average force exerted on your car during braking? (b) How far did you travel while braking?

A 65-kg skier speeds down a trail, as shown in Figure $5-26$. The surface is smooth and inclined at an angle of $22^{\circ}$ with the horizontal. Find the direction and magnitude of the net force acting on the skier.

As part of a physics experiment, you stand on a bathroom scale in an elevator. Though your normal weight is $610 \mathrm{~N}$, the scale at the moment reads $730 \mathrm{~N}$. What, if anything, can you say about the velocity of the elevator? Explain.

A 65-kg skier speeds down a trail, as shown in Figure . The surface is smooth and inclined at an angle of $22^{\circ}$ with the horizontal. Draw a free-body diagram for the skier.

A new-car dealer is leasing various brand-new randomly selected models for the monthly rates (in dollars) listed below. Estimate the true population variance (and standard deviation) in leasing rates with $90 \%$ confidence. Assume the variable is normally distributed.

$$\begin{array}{llllll}169 & 169 & 199 & 239 & 239 & 249\end{array}$$

A 5.0-kg bag of potatoes sits in a stationary shopping cart. (a) Sketch a free-body diagram for the bag of potatoes. (b) Now suppose the cart moves with a constant velocity. How does this affect your free-body diagram? Explain.