| Your Results | Global Average | |
|---|---|---|
| Questions | 5 | 5 |
| Correct | 0 | 3.16 |
| 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?
mechanical advantage |
|
conservation of mechanical energy |
|
work-energy theorem |
|
Pascal's law |
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.
| 70 ft⋅lb | |
| 140 ft⋅lb | |
| 1 ft⋅lb | |
| 0 ft⋅lb |
Friction resists movement in a direction __________ to the movement.
normal |
|
perpendicular |
|
opposite |
|
parallel |
Friction resists movement. Kinetic (also called sliding or dynamic) friction resists movement in a direction opposite to the movement. Because it opposes movement, kinetic friction will eventually bring an object to a stop. An example is a rock that's sliding across ice.
Which of these will have the most impact on the kinetic energy of an object?
its weight |
|
its mass |
|
its direction |
|
its speed |
Kinetic energy is the energy of movement and is a function of the mass of an object and its speed: \(KE = {1 \over 2}mv^2\) where m is mass in kilograms, v is speed in meters per second, and KE is in joules. The most impactful quantity to kinetic energy is velocity as an increase in mass increases KE linearly while an increase in speed increases KE exponentially.
| 0.88 | |
| 7 | |
| -1 | |
| 1.14 |
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 7 and the output radius (where the resistance is being applied) is 8 for a mechanical advantage of \( \frac{7}{8} \) = 0.88