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WorksheetsPLTW POE Unit 1 Quiz
Total questions: 28
Worksheet time: 14mins
A simple machine is a device that primarily:
Creates energy
Changes the magnitude or direction of a force
Converts heat to work
Increases speed only
Which list shows all six simple machines?
Lever, Wheel & Axle, Pulley, Inclined Plane, Wedge, Screw
Lever, Gear, Pulley, Ramp, Wedge, Cam
Wheel, Gear, Pulley, Lever, Wedge, Spring
Lever, Wheel, Pulley, Ramp, Wedge, Cylinder
Mechanical Advantage (MA) compares:
Input power to output power
Resistance (load) to effort
Distance to time
Rotational speed to torque
The correct formula for MA is:
MA = FE / FR
MA = FR / FE
MA = dE / dR
MA = L / h
Actual Mechanical Advantage (AMA):
Ignores friction
Is based on geometry only
Accounts for friction and real forces
Equals IMA for all machines
The correct formula for AMA is:
AMA = FE / FR
AMA = FR / FE
AMA = L / t
AMA = h / L
Ideal Mechanical Advantage (IMA):
Uses measured forces
Assumes no friction and uses dimensions/geometry
Uses motor specifications
Requires power data
Lever IMA is:
FR / FE
raxle / rwheel
dE / dR
L / h
Wheel & Axle IMA is:
rwheel / raxle
raxle / rwheel
dE / dR
L / t
Inclined Plane IMA is:
h / L
L / h
t / L
FR / FE
Wedge IMA is:
L / t
t / L
L / h
dE / dR
Screw IMA is:
2πr / pitch
pitch / 2πr
L / t
FR / FE
Pulley system IMA equals:
The number of pulleys
The number of supporting strands
Load ÷ effort
Height ÷ length
Pitch is defined as:
Threads per inch (TPI)
The distance between adjacent threads
Screw diameter
The slope of the thread
For a simple gear pair, gear ratio is:
Ndriven / Ndriver
Ndriver / Ndriven
τdriven / τdriver
ωdriver / ωdriven
If GR = Ndriver / Ndriven > 1, then the output gear typically:
Spins faster with less torque
Spins slower with more torque
Spins at the same speed and torque
Spins faster with more torque
Two gears are meshed: driver 10 teeth, driven 40 teeth. The GR equals:
0.25
1
2
4
For ideal gears, increasing GR (> 1) affects speed and torque as:
Speed ↑, torque ↑
Speed ↓, torque ↑
Speed ↑, torque ↓
Speed ↓, torque ↓
If the driver spins at 60 rpm and GR = 4, the driven speed is:
15 rpm
30 rpm
60 rpm
240 rpm
A class 1 lever has the fulcrum:
At the effort end
At the load end
Between effort and load
Off the lever
A class 2 lever always provides:
Speed advantage (MA<1)
Force advantage (MA>1)
No advantage (MA=1)
Changing fulcrum
A class 3 lever always provides:
Force advantage (MA>1)
Speed/distance advantage (MA<1)
No advantage (MA=1)
Equal arms
For any lever, IMA depends on:
Force ratio
Effort and resistance distances from fulcrum
Wheel radius only
Thread pitch only
Work is:
W = F × d (force parallel to motion)
W = F / t
W = m × g
W = P × t
The SI unit of work/energy is the:
Watt
Newton
Joule
Pascal
Potential Energy (gravitational) is given by:
PE = 1/2 mv^2
PE = mgh
PE = F × d
PE = τω
Kinetic Energy is given by:
KE = 1/2 mv^2
KE = mgh
KE = F × d
KE = P × t
Conservation of Energy means:
Machines create energy
Energy is destroyed as heat only
Energy cannot be created or destroyed, only transformed/transferred
Energy is always constant in every object
