| Your Results | Global Average | |
|---|---|---|
| Questions | 5 | 5 |
| Correct | 0 | 3.71 |
| Score | 0% | 74% |
| 520 ft. | |
| 2 ft. | |
| 32 ft. | |
| 1 ft. |
Win = Wout
Feffort x deffort = Fresistance x dresistance
In this problem, the effort work is 260 ft⋅lb and the resistance force is 130 lbs. and we need to calculate the resistance distance:
Win = Fresistance x dresistance
260 ft⋅lb = 130 lbs. x dresistance
dresistance = \( \frac{260ft⋅lb}{130 lbs.} \) = 2 ft.
On Earth, acceleration due to gravity (g) is approximately __________.
9.8 m/s2 |
|
1 m/s2 |
|
1 m/s |
|
6.67 x 10-11 m/s2 |
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.
What type of load acts on a relatively small area of a structure?
non-uniformly distributed load |
|
dynamic load |
|
impact load |
|
concentrated 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 surfaces would have the highest coefficient of friction?
concrete |
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marble |
|
steel |
|
ice |
Coefficient of friction (μ) represents how much two materials resist sliding across each other. Smooth surfaces like ice have low coefficients of friction while rough surfaces like concrete have high μ.
| 101.25 lbs. | |
| 135 lbs. | |
| 33.75 lbs. | |
| 240 lbs. |
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 Rb, our missing value, and plugging in our variables yields:
Rb = \( \frac{R_ad_a}{d_b} \) = \( \frac{30 lbs. \times 9 ft.}{8 ft.} \) = \( \frac{270 ft⋅lb}{8 ft.} \) = 33.75 lbs.