| Your Results | Global Average | |
|---|---|---|
| Questions | 5 | 5 |
| Correct | 0 | 3.14 |
| Score | 0% | 63% |
The work done by the sum of all forces acting on a particle equals the change in the kinetic energy of the particle. This defines which of the following?
conservation of mechanical energy |
|
Pascal's law |
|
mechanical advantage |
|
work-energy theorem |
The work-energy theorem states that the work done by the sum of all forces acting on a particle equals the change in the kinetic energy of the particle. Simply put, work imparts kinetic energy to the matter upon which the work is being done.
What defines the mechanical advantage of a first class lever?
output force |
|
position of the fulcrum |
|
input force |
|
output distance |
A first-class lever is used to increase force or distance while changing the direction of the force. The lever pivots on a fulcrum and, when a force is applied to the lever at one side of the fulcrum, the other end moves in the opposite direction. The position of the fulcrum also defines the mechanical advantage of the lever. If the fulcrum is closer to the force being applied, the load can be moved a greater distance at the expense of requiring a greater input force. If the fulcrum is closer to the load, less force is required but the force must be applied over a longer distance. An example of a first-class lever is a seesaw / teeter-totter.
On Earth, acceleration due to gravity (g) is approximately __________.
9.8 m/s2 |
|
1 m/s2 |
|
6.67 x 10-11 m/s2 |
|
1 m/s |
Newton's Law of Univeral Gravitation defines the general formula for the attraction of gravity between two objects: \(\vec{F_{g}} = { Gm_{1}m_{2} \over r^2}\) . In the specific case of an object falling toward Earth, the acceleration due to gravity (g) is approximately 9.8 m/s2.
| -5 | |
| 3 | |
| 2.67 | |
| 8 |
The mechanical advantage of a wheel and axle is the input radius divided by the output radius:
MA = \( \frac{r_i}{r_o} \)
In this case, the input radius (where the effort force is being applied) is 8 and the output radius (where the resistance is being applied) is 3 for a mechanical advantage of \( \frac{8}{3} \) = 2.67
| 0.18 | |
| 1.7 | |
| 0.2 | |
| 0.4 |
Mechanical advantage (MA) is the ratio by which effort force relates to resistance force. If both forces are known, calculating MA is simply a matter of dividing resistance force by effort force:
MA = \( \frac{F_r}{F_e} \) = \( \frac{4 ft.}{20.0 ft.} \) = 0.2
In this case, the mechanical advantage is less than one meaning that each unit of effort force results in just 0.2 units of resistance force. However, a third class lever like this isn't designed to multiply force like a first class lever. A third class lever is designed to multiply distance and speed at the resistance by sacrificing force at the resistance. Different lever styles have different purposes and multiply forces in different ways.