| Your Results | Global Average | |
|---|---|---|
| Questions | 5 | 5 |
| Correct | 0 | 3.49 |
| Score | 0% | 70% |
| 0.38 ft. | |
| 0.1 ft. | |
| 0.13 ft. | |
| 0.19 ft. |
To balance this lever the torques on each side of the fulcrum must be equal. Torque is weight x distance from the fulcrum so the equation for equilibrium is:
Rada = Rbdb
where a represents the left side of the fulcrum and b the right, R is resistance (weight) and d is the distance from the fulcrum.Solving for db, our missing value, and plugging in our variables yields:
db = \( \frac{R_ad_a}{R_b} \) = \( \frac{25 lbs. \times 1 ft.}{65 lbs.} \) = \( \frac{25 ft⋅lb}{65 lbs.} \) = 0.38 ft.
| 16 | |
| 8 | |
| 7.2 | |
| 2 |
The mechanical advantage (MA) of an inclined plane is the effort distance divided by the resistance distance. In this case, the effort distance is the length of the ramp and the resistance distance is the height of the green box:
MA = \( \frac{d_e}{d_r} \) = \( \frac{16 ft.}{2 ft.} \) = 8
The force amplification achieved by using a tool, mechanical device or machine system is called:
efficiency |
|
work |
|
power |
|
mechanical advantage |
Mechanical advantage is a measure of the force amplification achieved by using a tool, mechanical device or machine system. Such a device utilizes input force and trades off forces against movement to amplify and/or change its direction.
What type of load is sudden and for a relatively short duration?
dynamic load |
|
non-uniformly distributed load |
|
concentrated load |
|
impact load |
A concentrated load acts on a relatively small area of a structure, a static uniformly distributed load doesn't create specific stress points or vary with time, a dynamic load varies with time or affects a structure that experiences a high degree of movement, an impact load is sudden and for a relatively short duration and a non-uniformly distributed load creates different stresses at different locations on a structure.
Which of the following will increase the mechanical advantage of a second-class lever?
decrease the length of the lever |
|
move the object being lifted farther away from the fulcrum |
|
move the object being lifted closer to the fulcrum |
|
move the fulcrum between the force and the object being lifted |
A second-class lever is used to increase force on an object in the same direction as the force is applied. This lever requires a smaller force to lift a larger load but the force must be applied over a greater distance. The fulcrum is placed at one end of the lever and mechanical advantage increases as the object being lifted is moved closer to the fulcrum or the length of the lever is increased. An example of a second-class lever is a wheelbarrow.