9.4 Applications of statics, including problem-solving strategies  (Page 3/4)

When visiting some countries, you may see a person balancing a load on the head. Explain why the center of mass of the load needs to be directly above the person's neck vertebrae.

To get up on the roof, a person (mass 70.0 kg) places a 6.00-m aluminum ladder (mass 10.0 kg) against the house on a concrete pad with the base of the ladder 2.00 m from the house. The ladder rests against a plastic rain gutter, which we can assume to be frictionless. The center of mass of the ladder is 2 m from the bottom. The person is standing 3 m from the bottom. What are the magnitudes of the forces on the ladder at the top and bottom?

In [link] , the cg of the pole held by the pole vaulter is 2.00 m from the left hand, and the hands are 0.700 m apart. Calculate the force exerted by (a) his right hand and (b) his left hand. (c) If each hand supports half the weight of the pole in [link] , show that the second condition for equilibrium $\text{(net}{\tau }_{}=\text{0)}$ is satisfied for a pivot other than the one located at the center of gravity of the pole. Explicitly show how you follow the steps in the Problem-Solving Strategy for static equilibrium described above.

A child sits on the end of a playground see-saw. Which of the following values is the most appropriate estimate of the torque created by the child?

1. 6 N•m
2. 60 N•m
3. 600 N•m
4. 6000 N•m

A group of students is stacking a set of identical books, each one overhanging the one below it by 1 inch. They would like to estimate how many books they could place on top of each other before the stack tipped. What information below would they need to know to make this calculation?

1. The mass of each book
2. The width of each book
3. The depth of each book

1. I only
2. I and II only
3. I and III only
4. II only
5. I, II, and III

A 10 N board of uniform density is 5 meters long. It is supported on the left by a string bearing a 3 N upward force. In order to prevent the string from breaking, a person must place an upward force of 7 N at a position along the bottom surface of the board. At what distance from its left edge would they need to place this force in order for the board to be in static equilibrium?

1. $\frac{3}{7}$ m
2. $\frac{5}{2}$ m
3. $\frac{25}{7}$ m
4. $\frac{30}{7}$ m
5. 5 m

A bridge is supported by two piers located 20 meters apart. Both the left and right piers provide an upward force on the bridge, labeled F _L and F _R respectively.

1. If a 1000 kg car comes to rest at a point 5 meters from the left pier, how much force will the bridge provide to the left and right piers?
2. How will F _L and F _R change as the car drives to the right side of the bridge?

An object of unknown mass is provided to a student. Without using a scale, design an experimental procedure detailing how the magnitude of this mass could be experimentally found. Your explanation must include the concept of torque and all steps should be provided in an orderly sequence. You may include a labeled diagram of your setup to help in your description. Include enough detail so that another student could carry out your procedure.