1 / 14

Mechanical Power Transmission Fundamentals: Energy, Force, Inertia, Acceleration, Friction, and Work

This topic introduces the fundamentals of mechanical power transmission, covering concepts such as energy, force, inertia, acceleration, friction, and work. It references the textbook "Mechanical Principles and Systems for Industrial Maintenance" by Richard Knotek and Jon Stenerson.

kellymary
Download Presentation

Mechanical Power Transmission Fundamentals: Energy, Force, Inertia, Acceleration, Friction, and Work

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. MECH1200 Topics: • Introduction to Chapter 3: Mechanical Power Transmission Fundamentals • Energy • Force • Inertia • Acceleration • Friction • Work • Note: Refer to textbook Mechanical Principles and Systems for Industrial Maintenance, Richard Knotek and Jon Stenerson, Prentice Hall, 2006

  2. MECH1200 Introduction • Usually mechanical systems consist of the following elements: • A prime mover: such as en electric motor or an internal combustion engine. • Linking components: such as shafts, gears, belts, joints..etc. • Driven components such as wheels.

  3. MECH1200 Energy Exists in many forms: kinetic, potential, heat, electrical, chemical, ..etc. • Energy cannot be created nor destroyed, but it changes from one form to another. Law of conservation of energy - 1st law of thermodynamics • Some common units of energy: • Joule (J) • Foot-pound force (ft.lb) = 1.356 Joules • KiloWatt-hour (KWH) = 1000 Watt.h = 3600 kJ • Calorie = 4.2 kJ = 4200 J

  4. MECH1200 Force Force: causes an object that has a mass to change velocity. • A vector quantity: It has direction and magnitutde. • Some common units of force: Newton (N) Pound force (lbF) = 4.45 N

  5. MECH1200 Inertia • Inertia: the resistance of an object to any change in its motion state. • Example 1: Object A (1 kg) and object B (10 kg) are each acted upon by a force of 1 N to the right. which would move at a higher acceleration? A 1kg 1 N B 10 kg 1 N Object B has a larger inertia, thus more resistance to change in its rest state, so it has a lower acceleration.

  6. MECH1200 Newton’s Laws of Motion Newton’s First Law (Law of Inertia): A body in rest will stay in rest and a body in motion will stay in motion unless an external force is acted upon it. Newton’s Second Law (conservation of momentum): The net force acting on an object is equal to the rate of change of its momentum. Forcenet = mass × acceleration Newton’s Third Law (action-reaction law): For every action there is a reaction equal in magnitude and opposite in direction. FA = - FB

  7. MECH1200 Acceleration & Deceleration • The change of speed of a body. If the speed decreases, then it is a deceleration. • From Newton’s 2nd Law: • Example 2: • What is the acceleration of object A if a force of 2 N acts on it? • What is the acceleration of object B if a force of 20 N acts on it? A 1kg 2 N B 10 kg 20 N Both objects will move at the same acceleration and acquire the same final speed. Both objects will have an acceleration of 2 m/s2

  8. MECH1200 Acceleration & Deceleration • Example 3: • A vehicle is moving at a speed of 20 ft/s. After 4 seconds, the vehicle was moving at a speed of 15 ft/s. what is the acceleration of the vehicle? • Solution: Thus the vehicle decelerates by 1.25 ft/s2.

  9. MECH1200 Angular Speed • Angular speed: a measurement to describe an object rotating about an axis. • Units of measurement: • RPM • Rad/s Surface velocity (ft/min) = RPM× π × diameter (ft) = RPM ×0.262 × diameter (in inches) Example 4: what is the surface velocity of a 20 in diameter rotor that rotates at 1500 rpm? Solution: = 1500 × 0.262 × 20 = 7860 ft/min

  10. MECH1200 Friction • The resistance to a mechanical force. • Applies to solids and fluids • Types of friction: • Static friction: when the contacting surfaces are at rest. • Sliding friction: when one or both of contacting surfaces is/are at motion. • Rolling friction: when the surfaces are separated by rollers. How to quantify friction? Coefficient of friction relates force to mass of object under force.

  11. MECH1200 Work • Work = force × distance ( W = F × D) • Units of work: N.m or ft.lb • Example 5: • A force of 10 ft.lb is applied on a body at rest that has a mass of 4 lb. Then the force was removed after the body moved 5 ft. 4 kg 10 N What is the acceleration that the body acquires while the force is applied? F = ma thus a = F/m = 10 / 4 = 2.5 ft/s2 b) What is the work performed on the body? W = F×D = 10 × 5 = 50 ft.lb

  12. MECH1200 Exercise 1. Which of the following are vectors and which are scalar quantities: Temperature Pressure Velocity Acceleration Energy Force Inertia scalar scalar vector vector scalar vector scalar

  13. MECH1200 Exercise 2. Match each of the following terms to its unit of measurement: Mass Energy Velocity Acceleration Force Power Angular speed Kilowatt.hour Newton kilowatt ft/s Kg RPM m/s2

  14. MECH1200 Exercise 3. What is the acceleration (g) of the earth’s gravitational force at sea level? Solution: 9.81 m/s2 = 32.2 ft/s2

More Related