Transcript U3-2 ME 1 - Levers_ Inclined Plane

Unit 3: Engineering Design
Get out last night’s Homework assignment
A rope is used to pull a metal box 15 m across the floor
in 34 seconds. The rope is held at an angle of 45o with
the floor and a force of 628 N is used. How much work
does the force on the rope do? How much power is
consumed? How efficiently is the force being applied
to move the metal box?
Unit 3: Engineering Design
Topics Covered
1.
2.
3.
4.
5.
6.
Force, Energy, Work, Power, and Efficiency
Topics in Mechanical Engineering
Topics in Electrical Engineering
Engineering Design Process
Teams and Projects
PROJECT: Mechanically Controlled Electromagnetic Crane
Unit 3 Quiz 1 – 12/01/10
Use the Problem Solving Process to Solve and show all work:
A rope is used to pull a metal box 10 m across the floor in 30
seconds. The rope is held at an angle of 60o with the floor
and a force of 600 N is used. How much work does the force
on the rope do? How much power is consumed? How
efficiently is the force being applied to move the metal box?
2A. How much work is required to lift a 50 N box to a height of
3 m?
2B. What is the gravitational potential energy of the box once it
has been lifted?
2C. If the box is dropped from that height, how fast is it
travelling when it hits the ground?
1.
Simple Machines
1.
Machines:
1.
2.
2.
Devices that use energy to transmit power, force, or motion
Input and Output
Simple Machines:
1.
2.
Devices that transform the direction or magnitude of a force
without consuming additional energy
6 simple machines:
Lever: Lever, Wheel and Axle, Pulley
Inclined Plane: Inclined Plane, Wedge, Screw
LEVERS
1.
Components:
1.
2.
3.
4.
2.
Bar/rod
Fulcrum/pivot
Applied Force
Load
Principle of the Lever:
1.
Static Equilibrium Demonstration
1. SF = 0 – Sum of Forces equals 0
2. SM = 0 – Sum of Moments equals 0
2.
F x dF = L x dL
3rd Class
2nd Class
LEVERS
1.
A 1380-kg car is sitting on a hill in neutral. The angle the hill makes
with the horizontal is 30o. The distance from flat ground to the car
is 200 m. What is the potential energy of the car? How efficient is
the force of gravity being applied to the vehicle? What is the work
done on the car by gravity? What is the kinetic energy of the car
when it reaches the bottom of the hill? What is the velocity of the
car when it reaches the bottom of the hill?
2.
The manager of a theater knows that 900 tickets were sold for a
certain performance. If orchestra tickets sold for $3 each and
balcony tickets for $2 each, and if the total receipts were $2300,
how may of each kind of ticket were sold?
3.
The sum of the digits of a number is 9. If the digits are reversed,
the number is increased by 45. What is the original number?
UNIT 2: Engineering Communication
TEST TOMORROW
Topics:
1. Types of Communication Technology
2. Technical Drawing Types (distinguish between them)
3. Draw Isometric drawing on Iso graph paper
4. Draw missing orthographic lines
5. Solve 2 word problems (systems of equations)
INCLINED PLANE
1.
Inclined Plane
Slanted surface used to raise an object
2.
Wedge
1.
2.
3.
3.
Double-sided inclined plane
Used to split, separate, grip
Wood chisel, firewood axe, doorstop
Screw
1.
2.
Inclined plane wound around a central shaft
Identified by diameter and threads per inch
H
D
What’s the point???
Mechanical Advantage
1.
W=Fxd
Which path takes less work?
1.
2.
2.
3.
4.
Climbing the steep, short cliff face or
Walking the longer, less steep path
It will always take a certain amount of work to lift an
object a specific height.
The energy required to perform a task will not change.
We can alter how we do the work or apply the energy.
Mechanical Advantage
1.
MA
1.
2.
3.
4.
Force Multiplier: the number of times a mechanical device
multiplies the applied force.
Distance Multiplier: “ the distance the applied force travels.
Let F = 5kg, L = 100kg, and dF = 100cm. What is dL?
1. Is this a force multiplier or a distance multiplier?
2. How many times is the applied force multiplied?
Equation:
1. MA = L / F
H
D
2. MA = dF / dL
WHEEL and AXLE
1st, 2nd, 3rd Class Lever
WHEEL and AXLE
1st, 2nd, 3rd Class Lever
Mechanical Advantage
Homework
1.
Use dimensional reasoning (and the power-law
expression) to determine expressions for the terms on
the left side of the equations:
1. W = f(F, d)
2. P = f(F, d, t)
3. F = f(m, a)
4. Eff = f(output, input)
QUIZ – 1 Problem, 6 parts – 2009 SY
Show ALL problem solving steps
a) How much work is required to lift a 100-kg box to a height of 1m?
b) Now what is the gravitational potential energy of the load?
c) If the load is dropped from that height, how fast is it travelling
when it hits the ground?
d) If a system with a mechanical advantage of 4 is used to lift the load
that distance, what is the required applied force?
e) How far must that applied force travel in order to move the load
the distance of 5m?
f) If the applied force is in the direction of the displacement, what is
the efficiency of the system?