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 45 o 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 Get out last night’s Homework assignment

Topics Covered 1. Force, Energy, Work, Power, and Efficiency 2. Topics in Mechanical Engineering 3. Topics in Electrical Engineering 4. Engineering Design Process 5. Teams and Projects 6. PROJECT: Mechanically Controlled Electromagnetic Crane Unit 3: Engineering Design

1. 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 60 o 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? Unit 3 Quiz 1 – 12/01/10 Use the Problem Solving Process to Solve and show all work:

1. Machines: 1. Devices that use energy to transmit power, force, or motion 2. Input and Output 2. Simple Machines: 1. Devices that transform the direction or magnitude of a force without consuming additional energy 2. 6 simple machines: Lever: Lever, Wheel and Axle, Pulley Inclined Plane: Inclined Plane, Wedge, Screw Simple Machines

1. Components: 1. Bar/rod 2. Fulcrum/pivot 3. Applied Force 4. Load 2. Principle of the Lever: 1. Static Equilibrium Demonstration 1. S F = 0 – Sum of Forces equals 0 2. S M = 0 – Sum of Moments equals 0 2. F x d F = L x d L LEVERS 2 nd Class 3 rd Class

LEVERS

1. A 1380-kg car is sitting on a hill in neutral. The angle the hill makes with the horizontal is 30 o. 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?

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) UNIT 2: Engineering Communication

1. Inclined Plane Slanted surface used to raise an object 2. Wedge 1. Double-sided inclined plane 2. Used to split, separate, grip 3. Wood chisel, firewood axe, doorstop 3. Screw 1. Inclined plane wound around a central shaft 2. Identified by diameter and threads per inch INCLINED PLANE D H

What’s the point???

W = F x d 1. Which path takes less work? 1. Climbing the steep, short cliff face or 2. Walking the longer, less steep path 2. It will always take a certain amount of work to lift an object a specific height. 3. The energy required to perform a task will not change. 4. We can alter how we do the work or apply the energy. Mechanical Advantage

1. MA 1. Force Multiplier: the number of times a mechanical device multiplies the applied force. 2. Distance Multiplier: “ the distance the applied force travels. 3. Let F = 5kg, L = 100kg, and d F = 100cm. What is d L ? 1. Is this a force multiplier or a distance multiplier? 2. How many times is the applied force multiplied? 4. Equation: 1. MA = L / F 2. MA = d F / d L Mechanical Advantage D H

WHEEL and AXLE 1 st, 2 nd, 3 rd Class Lever

Mechanical Advantage

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) Homework

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? QUIZ – 1 Problem, 6 parts – 2009 SY Show ALL problem solving steps