MA Part 1
*Define mechanical advantage.
Mechanical advantage is how many times a machine multiplies force
*You have a load that is 100N, in which you input 50N of effort.
What is the Mechanical Advantage?
The mechanical advantage is of 2
Output Force / Input Force = MA
100 ÷ 50 = 2
*What does Speed Ratio measure?
Speed Ratio compares input distance to output distance
* You have a wheelchair that you want to push up a ramp 10m in the park, the height of the ramp is 2m, what is the Speed Ratio?
The Speed Ratio is of 5
Input Distance/ Output Distance= SR
10 ÷ 2 = 5
*What does friction mean?
Friction is a force that opposes motion.
*What does Mechanical Advantage greater than 1 mean?
Mechanical Advantage greater than 1 mean that output force is greater than input (force advantage)
* You have a 300N gear moving by a driver gear pushing with 100N effort, what is the Mechanical Advantage?
The mechanical advantage is of 3
Output Force / Input Force = MA
300 ÷ 100 = 3
*What does HIGH Speed Ratio mean?
It means that the input distance moves much farther than output distance.
* You have to save a friend from a hole. You hav a pulley, and pull your friend up with a rope. You pull 8m ropes, which lifts your friend 2m, what is the Speed Ratio?
The Speed Ratio is of 4
Input Distance/ Output Distance= SR
8 ÷ 2 = 4
*Where does lost energy goes?
Lost energy is usually lost as heat
*What does a Mechanical Advantage of 1 mean?
A Mechanical Advantage of 1 means that there is no force gain, only a change in direction.
You are working out and pushing a box up a hill. You are pushing with a force of 120N, but the box is about 90N. What is the Mechanical Advantage, and what does that number mean?
Output Force / Input Force = MA
90 ÷ 120 = 0.75
→ Less than 1 = no force advantage (speed/distance advantage)
*Would a car have the a Mechanical Advantage equal to its speed ratio and why?
No, because SR is an Ideal Mechanical Advantage, and MA loses energy due to friction.
*You have a driver gear with 10 teeth moving a gear with 50 teeth, what is the Speed Ratio?
The Speed Ratio is of 5
50 teeth ÷ 10 teeth = 5
*A new machine that was invented was used in a hospital for the first time. It has a Mechanical Advantage of 2, and it has a Speed Ratio of 4, what is the efficiency of the machine?
The Efficiency is of 50%
Eff= (MA/SR)x100%
(2 ÷ 4) × 100 = 50%
*Why are there no units in Mechanical Advantage, and Speed Ratio?
There are no units because it’s a ratio
(force ÷ force) = 1
(distance ÷ distance) = 1
With a pulley, you lift a load upwards. You get a Mechanical Advantage of 0.5, and youre putting 200N of energy to lift the load. What is the force of the load in the system?
The Output Force (Load) is of 100N
Output Force / Input Force = MA
MA x Input Force = Output Force
Load = 0.5 × 200 = 100 N
*Why is Speed Ratio not affected by friction?
Because it only depends on distances, not forces
*You are going up a ramp with your skateboard. The elevation of the ramp is of 2 meters. You have a Speed Ratio of 5. What is the Input distance?
The Input Distance is of 10m
Input Distance/ Output Distance= SR
SR x Output Distance = Input Distance
Distance = 5 × 2 = 10 m
*A car has an Efficiency of 50%, its Speed Ratio was calculated to be 6. What is the car Mechanical Advantage?
The Mechanical Advantage is of 3
Eff= (MA/SR)x100%
MA = (Eff/100%) x SR
MA = 0.5 × 6 = 3
*Why is it that Mechanical Advantage reduces speed?
Because increasing force advantage trades off distance/speed
By using a lever to lift up a car, you use 25N of force to lift it up, which gives you a Mechanical Advantage of 4. What is the load of the car?
The Output Force is of 100N
Output Force / Input Force = MA
MA x Input Force = Output Force
Load = 4 × 25 = 100 N
*Why is Speed Ratio the Ideal Mechanical Advantage?
Because it represents an ideal conditions (no friction)
* You lift a box to put into your moving truck using a pulley system. You lift up the box 3 meters off the ground, but it has a Speed Ratio of 4, How much rope did you pull?
The Input Distance is of 12m
Input Distance/ Output Distance= SR
SR x Output Distance = Input Distance
Distance = 4 × 3 = 12 m
* A bicycle gear has a Mechanical Advantage of 1.8, and has a Speed Ratio of 6, what is the efficiency percentage, and the percentage loss?
The Efficiency is of 30%
Eff= (MA/SR)x100%
(1.8 ÷ 6) × 100% = 30%
Energy lost = 70%