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# 5.1: Unit 5 Practice and Assessment

#### 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.

1. 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.

1. 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

1. 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.

1. 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

2. Each structure in the following image is at rest. What do you know about the net force on each block?

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.

1. Structure #1 weighs 5000 N. What is the normal force on the structure?
2. 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?
3. Structure # 4 weighs 5000 N. Each rocket is capable of pushing with 1000 N of force. What is the tension force provided by the rope?
4. The structure in the following image is at rest. What do you know about the net torque on the structure?

An inverted triangular structure at rest with a block weighting one side, an arm weighting the other, and a rocket pushing up on the arm. Rocket images from http://wpclipart.com are in the Public Domain.

1. An engineer performing an inspection on the previous structure measures 45 m from beneath the center of gravity of the block to the point where the structure contacts the ground. The block weighs 1200 N. She then measures the distance to the beneath the center of gravity of the arm to be 95 m. The arm weighs 1200 N as well. Finally she measures the distance to beneath the rocket to be 150 m from the contact point. She then calculates the force being provided by the rocket, what value does she get?

#### Outcome 4

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

Four structures in static equilibrium

#### Outcome 5

1. 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.