...Module 1 Force And Friction A force is a push or pull upon an object resulting from the object's interaction with another object. Whenever there is an interaction between two objects, there is a force upon each of them. When the interaction ceases, the two objects no longer experience the force. Forces only exist as a result of an interaction. Force is a quantity which is measured using the standard metric unit known as the Newton. [pic] For simplicity sake, all forces (interactions) between objects can be placed into two broad categories: • contact forces, and • forces resulting from action-at-a-distance Contact forces are those types of forces which result when the two interacting objects are perceived to be physically contacting each other. Examples of contact forces include frictional forces, tensional forces, normal forces, air resistance forces, and applied forces. Action-at-a-distance forces are those types of forces which result even when the two interacting objects are not in physical contact with each other, yet are able to exert a push or pull despite their physical separation. Examples of action-at-a-distance forces include gravitational forces. For example, the sun and planets exert a gravitational pull on each other despite their large spatial separation. Even when your feet leave the earth and you are no longer in physical contact with the earth, there is a gravitational pull between you and the Earth. Electric...
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...Friction is what happens when any two things rub against each other. These can be solid things, like your two hands rubbing together, or your skis rubbing on the snow, or a hammer hitting a nail, or they can be gases, like friction with the air slowing down your car, or liquids, like friction with the water slowing down a boat. Nobody completely understands what causes friction. Partly, friction happens when the rough edges of one object snag on the rough edges of another object, and some of the objects' energy has to be used to break off those rough edges so the objects can keep moving. And when you rub two soft things together, like your hands, sometimes they squish into each other and get in each other's way. But even completely smooth, hard things have some friction. This friction is the result of the molecules in both objects being attracted to each other. We know how to make more friction or less friction, and how to predict how much friction there will be. There's more friction when the two objects are pushed together harder. If you push your hands together, it's harder to rub them up and down. If you pull the brake lever harder, your bike will stop faster. Because gravity pulls harder on things with more mass, things with more mass have more friction and are harder to move - a cube of iron will be harder to move than a cube of wood. Two solid things usually have more friction than two liquid things, or one liquid thing and a solid - that's why you slip on a wet surface...
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...the crate exerts on the person. [(a) 1.13 x 103 N, (b) 735 N] 3. A worker stands still on a roof sloped at an angle of 45° above the horizontal. He is prevented from slipping by a static frictional force of 450 N. Find the mass of the worker. [85 kg] 4. A 4.0-kg bucket of water is raised from a well by a rope. If the upward acceleration of the bucket is 5.0 m/s2, find the force exerted by the rope on the bucket. [59 N] 5. A block is pressed against a vertical wall by a force [pic], as the drawing shows. This force can either push the block upward at a constant velocity or allow it to slide downward at a constant velocity. The magnitude of the force is different in the two cases, while the directional angle ( is the same. Kinetic friction exists...
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...crate exerts on the person. [(a) 1.13 x 103 N, (b) 735 N] 3. A worker stands still on a roof sloped at an angle of 45° above the horizontal. He is prevented from slipping by a static frictional force of 450 N. Find the mass of the worker. [85 kg] 4. A 4.0-kg bucket of water is raised from a well by a rope. If the upward acceleration of the bucket is 5.0 m/s2, find the force exerted by the rope on the bucket. [59 N] 5. A block is pressed against a vertical wall by a force [pic], as the drawing shows. This force can either push the block upward at a constant velocity or allow it to slide downward at a constant velocity. The magnitude of the force is different in the two cases, while the directional angle ( is the same. Kinetic...
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...Physics Lab 4 Part 1: Friction Parabola Track 3a. Kinetic energy is the highest when the skate board has reached its lowest point. 3b. Kinetic energy is the lowest when in the middle of the drop. 4a. Potential energy is the highest when the skate board has reached the highest point. 4b. Potential energy is lowest when in the middle of the drop. 5a. Total energy is the highest when potential energy is at its highest point. 6. The value of thermal energy is 0 only when potential energy is highest. David Del Rio Physics PH 2530 Lab 4 Energy 04/06/2015 Part 1: Loop Track 8. When a skateboarder moves, what happens to the kinetic and potential energy? Conservative (closed) or non-conservative (open) system? - Kinetic energy rises as the skateboarder moves downward. -potential energy rises as the skateboarder moves up. - Non-Conservative 9. Where is the skateboarder at on the ramp when he reaches the maximum point of potential energy? 4546.93 11. m = 76./kg The skateboarders mass = 76 kg 12a. calculated mass = 76 kg 12b. Actual mass 75 kg 12c. Comparison = .98% 13. When the coefficient is adjusted half way the kinetic energy decreases to 0 as to the potential energy decreases and finally stabilizes. - This is a closed system. Part 2: Friction Parabola Track 2a. kinetic energy is highest when the skaters’ board is at the lowest point 2b. in the middle of the drop the kinetic energy is highest. 3a. potential energy is the highest when the skaters’...
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...|Lecturer |: Kevin Chin | |Session |: 201605 | | | Additional Tutorial 4: Work and Energy. 1. A push of 120 N is applied along the handle of a lawn mower producing a horizontal displacement of 14.0 m. If the handle makes an angle of 30.0o with the ground, what work was done by the 120 N force? [1.45×103 J] 2. A box of mass 5.0 kg is accelerated by a force across a floor at a rate of 2.0 m/s2 for 7.0 s. Find the net work done on the box. [490 J] 3. What is the minimum work needed to push a 950-kg car 810 m up along a 9.0º incline? (a) Ignore friction. (b) Assume the effective coefficient of friction retarding the car is 0.25. [(a) 1.2×106 J, (b) 3.0×106 J] 4. The net force exerted on a particle acts in the +x direction. Its magnitude increases linearly from zero at x = 0 to 24.0 N at x = 3.0 m. It remains constant at 24.0 N from x = 3.0 m to x = 8.0 m and then decreases linearly to zero at x = 13.0 m. Determine the work done to move the particle from x = 0 to x = 13.0 m graphically by determining the area under the Fx vs x graph. [216 J] 5. If the speed of a car is increased by 50%, by what factor will its minimum braking distance be increased, assuming all else is the same? Ignore the driver’s reaction time. [2.25] 6. Two blocks are connected by a light string that...
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...KINEMATICS 1. INTRODUCTION TO KINEMATICS Dynamics is the study of moving objects. The subject is divided into kinematics and kinetics. Kinematics is the study of a body’s motion independent of the forces on the body. It is the study of the geometry of motion without consideration of the causes of motion. Kinematics deals only with relationships among the position, velocity, acceleration, and time. Kinetics deals with both forces and motion. 2. PARTICLES AND RIGID BODIES Bodies in motion can be considered particles if rotation is absent or insignificant. Particles do not possess rotational kinetic energy. All parts of a particle have the same instantaneous displacement, velocity, and acceleration. A rigid body does not deform when loaded and can be considered as a combination of two or more particles that remain at a fixed, finite distance from each other. 3. COORDINATE SYSTEMS The position of a particle is specified with reference to a coordinate system. A coordinate can represent a position along an axis, as in the rectangular coordinate system or it can represent an angle, as in the polar, cylindrical, and spherical coordinate systems. In general, the number of degrees of freedom is equal to the number of coordinates required to completely specify the state of an object. If each of the coordinates is independent of the others, the coordinates are shown as holonomic coordinates. 4. CONVENTIONS OF REPRESENTATION ...
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...Question 5 | | 1 / 1 point | In the figure shown, the coefficient of kinetic friction between the block and the incline is 0.40. What is the magnitude of the acceleration of the suspended block as it falls? Disregard any pulley mass or friction in the pulley. Question options: | 1) | 3.4 m/s2 | | | 2) | 3.7 m/s2 | | | 3) | 4.2 m/s2 | | | 4) | 3.9 m/s2 | | | 5) | 5.4 m/s2 | | Question 34 | | 1 / 1 point | A 4.0-kg block slides down a 35 incline at a constant speed when a 16-N force is applied acting up and parallel to the incline. What is the coefficient of kinetic friction between the block and the surface of the incline? Question options: | 1) | 0.20 | | | 2) | 0.23 | | | 3) | 0.26 | | | 4) | 0.33 | | | 5) | 0.41 | | Question 35 | | 1 / 1 point | A 1.0-kg block is pushed up a rough 22 inclined plane by a force of 7.0 N acting parallel to the incline. The acceleration of the block is 1.4 m/s2 up the incline. Determine the magnitude of the force of friction acting on the block. Question options: | 1) | 1.9 N | | | 2) | 2.2 N | | | 3) | 1.3 N | | | 4) | 1.6 N | | | 5) | 3.3 N | | Question 40 | | 1 / 1 point | A 2.0-kg object has a velocity of 4.0i m/s at t = 0. A constant resultant force of (2.0i + 4.0j) N then acts on the object for 3.0 s. What is the magnitude of the object's velocity at the end of the 3.0-s interval? Question options: | 1) | 9.2...
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...Force Diatra Farasha In physics, a force is any influence that causes an object to undergo a certain change, either concerning its movement, direction, or geometrical construction. It is measured with the SI unit of newtons and represented by the symbol F. In other words, a force is that which can cause an object with mass to change its velocity (which includes to begin moving from a state of rest), i.e., to accelerate, or which can cause a flexible object to deform. Force can also be described by intuitive concepts such as a push or pull. A force has both magnitude and direction, making it a vector quantity. The original form of Newton's second law states that the net force acting upon an object is equal to the rate at which its momentum changes. This law is further given to mean that the acceleration of an object is directly proportional to the net force acting on the object, is in the direction of the net force, and is inversely proportional the mass of the object. As a formula, this is expressed as: Related concepts to force include: thrust, which increases the velocity of an object; drag, which decreases the velocity of an object; and torque which produces changes in rotational speed of an object. Forces which do not act uniformly on all parts of a body will also cause mechanical stresses, a technical term for influences which cause deformation of matter. While mechanical stress can remain embedded in a solid object, gradually deforming it, mechanical stress in a fluid...
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...iv. Pulley v. Paperclips (weights) vi. Safety goggles 3. Procedure a. (Part 1)-determine kinetic friction between the wooden block and the wooden board b. Read through the entire procedure and prepare to carefully collect your data before you begin. c. Before assembling the materials, prepare a clean, dry workspace (away from food) with all necessary materials. d. Weigh and record the mass of the wooden block. e....
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...Experiment #6-FREE FALL FALLING BODIES OBJECTIVES: 1.To describe how the velocity and acceleration of an object change over time when falling under the influence of gravity and to explain why such changes are observed. 2. To determine gravitational acceleration by studying the velocity of a falling object as a function of time. INTRODUCTION: Everything on Earth is under the influence of it’s gravitational field keeping us from jumping of respected measure high.Along with this things that are on Earth,there are objects that are soon to be on Earth’s surface,falling objects have certain interactions with Earth’s gravity.Air resistance is a factor of free-falling objects.Since Earth has an atmosphere,the speed of which objects fall at are not constant. While you are falling, you will probably feel as if you are floating—or not even moving at all. Falling is relational—if there is nothing to fall toward, you may not even be aware that you’re falling. If there is no ground, gravity might be low and you’ll feel weightless. Objects will stay suspended if you let go of them. Whole societies around you may be falling just as you are. And it may actually feel like perfect stasis—as if history and time have ended and you can’t even remember that time ever moved forward. A free falling object is an object that is falling under the sole influence of gravity. Any object that is being acted upon only by the force of gravity is said to be in a state of free fall. ...
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...UNIT 2 FRICTION Structure 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 Introduction Objectives Friction Types of Friction Laws of Dry Friction Static and Kinetic Friction Coefficient of Friction Angle of Repose Least Force Required to Drag a Body on a Rough Horizontal Plane Horizontal Force Required to Move the Body Screw and Nut Friction 2.10 Self-Locking Screws 2.11 Condition for Maximum Efficiency 2.12 Screw Jack 2.13 Pivot and Collar Friction 2.13.1 Flat Pivot 2.13.2 Conical Pivot 2.13.3 Collar Bearing 2.14 Clutch 2.15 Types of Clutches 2.15.1 Conical Clutch 2.15.2 Single Plate Clutch 2.15.3 Multi Plate Clutch 2.16 Journal Bearing 2.17 Rolling Friction 2.18 Ball and Roller Bearings 2.19 Summary 2.20 Key Words 2.21 Answers to SAQs 2.1 INTRODUCTION When a body moves or tends to move on another body, a force appears between the surfaces. This force is called force of friction and it acts opposite to the direction of motion. Its line of action is tangential to the contacting surfaces. The magnitude of this force depends on the roughness of surfaces. In engineering applications friction is desirable and undesirable. We can walk on the ground because of friction. Friction is useful in power transmission by belts. It is useful in appliances like brakes, bolts, screw jack, etc. It is undesirable in bearing and moving machine parts where it results in loss of energy and, thereby, reduces efficiency of the machine. In this unit, you will study screw jack, clutches and...
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...block is dragged by a force ¢ along a rough steel plate, as shown below for two cases. The magnitude of the applied force ¢ is the same for both cases. The normal force in (ii), as compared with the normal force in (i) is:| A)|the same| B)|greater| C)|less| D)|less for some angles of the incline and greater for others| E)|less or greater, depending on the magnitude of the applied force ¢.| 4.|A 6-kg object is moving south. A net force of 12 N north on it result in the object having an acceleration of: | A)|2 m/s2, north | B)|2 m/s2, south | C)|6 m/s2, north | D)|18 m/s2, north | E)|18 m/s2, south | 5.|A 9000 N automobile is pushed along a level road by four students who apply a total forward force of 500 N. Neglecting friction, the acceleration of the automobile is: | A)|0.055m/s2| B)|0.54 m/s2| C)|1.8 m/s2| D)| 9.8 m/s2| E)|18 m/s2| 6.|A 25-kg crate is pushed across a frictionless horizontal floor with a force of 20 N, directed 20° below the horizontal. The acceleration of the crate is: | A)|0.27 m/s2| B)|0.75 m/s2| C)|0.80 m/s2| D)|170 m/s2| E)|470 m/s2| 7.|Two forces are applied to a 5.0-kg crate; one is 6.0 N to the north and the...
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...12.2 RrcrrLrrueaR Krrueuerrcs: Corurrruuous 15 MorroN It is highly suggested that you test yourself on the solutions to these examples, by covering them over and then trying to think about which equations of kinematics must be used and how they are applied in order to determine the unknowns. Then before solving any of the problems, try and solve some of the Fundamental Problems given below. The solutions and answers to all these problems are given in the back of the book. Doing this throughout the book will help immensely in understanding how to apply the theory, and thereby develop your problem-solving skills. Fa2-1. Initially, the car travels along a straight road with a speed of 35 m/s. If the brakes are applied and the speed of the car is reduced to 10 m/s in 15 s, determine the constant deceleration of the car. F12-5. The position of the particle is given by s : Q? - 8/ + 6) m, where r is in seconds. Determine the time when the velocity of the particle is zero, and the total distance traveled by the particle when r : 3 s. ,t,t.tO F7Z-1 Fl2-5 Fa2-2. A ball is thrown vertically upward with a speed of l5 m/s. Determine the time of flight when it returns to its original position. Fl2-6. A particle travels along a straight line with an acceleration of ,, : (10 - 0.2s) m/s2, where s is measured in meters. Determine the velocity of the particle when s: lOmif u:5m/sats:0. 6 _s 1' F12-6 Ftz-z Fl2-7. A particle FI2-3. A particle travels along a straight line...
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...School of Engineering and Design SED06: Examinations Cover Sheet SUBJECT AREA: MECHANICAL ENGINEERING Module Code: Module Title: ME1301 THERMOFLUIDS Date-Month: MAY Year: 2011 Time allowed Hours: THREE Answer FOUR questions: TWO from Section A, TWO from Section B. Examiner(s): Dr T Megaritis and Dr R Kirby Special Stationery Requirements: Thermodynamic and Transport Properties of Fluids, GFC Rogers and YR Mayhew. Only School approved calculators are allowed. Use a separate answer book for each section. If you submit answers to more questions than specified, final marks for the examination will be determined using the best marks which satisfy the rubric. - 1 ___________________________________________________________________________ SECTION A A1. (a) Define what is meant by a streamline, a pathline, a streakline and a streamtube. When are the streamlines, pathlines and streaklines identical? [25%] Write down Bernoulli’s equation and define all the terms that appear in the equation. [20%] Water flows vertically upwards through a pipe which tapers from a cross-sectional area of 0.3 m2 at section A to 0.15 m2 at section B. Section B is located 6 m above section A. At A the flow velocity is 1.8 m/s and the static pressure is 117 kN/m2. Neglecting all losses, determine: (i) (ii) (iii) The water volumetric and mass flow rates. The velocity of water at section B. The water static pressure at section B. [15%] [15%] [25%] (b) (c) DATA Gravitational...
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