Outcome 1

1) Rank the structures below in order of increasing support base width.

Four structures of equal height, but varying shape and base width.

2) Rank the structures below in order of increasing center of gravity height. All four structures are solid and are made of the same material.

Four structures of equal mass, but varying height and base width.

3) Rank the structures below in order of increasing normal force from the ground. All four structures have the same weight and are at rest.

Four structures of equal weight. The second structure has rockets pushing up on it and the fourth structure is hanging from a rope. Rocket images  from http://wpclipart.com are in the Public Domain.

Outcome 2

5) A child at a playground pushes on a large disk that rotates on an axle trough its center.  The child tries pushing on the edge of the disk in several different directions, as indicated by the top-down diagrams below.  Rank the child’s attempts by the amount of torque applied to the disk, from least to greatest.

Four disks 0.5 m radius, each with a 12 N force applied at the edge. Disk 1 has the force applied outward at a slight angle to the radius. Disk two has the force applied outward directly along the radius. Disk 3 has the force applied perpendicular to the radius. Disk four has the force applied at a slight angle to the radius, but inward. The angle with the radius is smaller than the angle in disk 1.

6) If the child in the previous problem was able to apply a 12 N force and the disk had a 0.5 m radius, what would be the value of the torque applied in trial 3?

Outcome 3

7) State which type of equilibrium is exhibited by each structure below: stable, unstable, or metastable.

Four structures in static equilibrium

8) Rank the structures below in order of increasing stability. All structures are solid and made of a single material type.

Four structures in metastable equilibrium.

Outcome 4

9) A car with a weight of 10,000 N is sitting on concrete with the parking brake on.

a) What is the net force on the car?

b) What is the net torque on the car?

10) What is the normal force from the concrete on the car from exercise 9?

b) What is the maximum horizontal force that can be applied before the car begins to skid? List your sources for the friction coefficient.

c) After the car begins to skid, how much force is required to keep it moving at constant speed, despite kinetic friction?

d) If  you apply only 120 N of horizontal force to the stationary car, what is the static frictional force at that time?

11) Each structure in the following image is at rest.

a) What do you know about the net force on each block?

b) Structure #1 weighs  5000 N. What is the normal force on the structure?

c) Structure # 2 weighs 5000 N. Each rocket is capable of pushing with 1000 N of force. What is the normal force on the structure from the ground?

d) Structure # 4 weighs 5000 N. The rocket is capable of pushing with 1000 N of force. What is the tension force provided by the rope?

Four structures of equal weight. The second structure has rockets pushing up on it and the fourth structure is hanging from a rope. Rocket images  from http://wpclipart.com are in the Public Domain.