When released, the lift provides a net force of 6 N on a 2 kg balloon. If it started at rest, how fast will it be moving in 4.0 s? F net = 6 Nm = 2 kg.

Slides:



Advertisements
Similar presentations
Dr. Steve Peterson Physics 1025F Mechanics NEWTON’S LAWS Dr. Steve Peterson
Advertisements

Forces In One Dimension.
Chapter 4 Forces.
Force Force is a push or pull on an object The object is called the System Force on a system in motion causes change in velocity = acceleration Force is.
Newton’s 2nd Law some examples
Laws of Motion Review.
Newton’s Laws.
Forces and The Laws of Motion
Weight is a force that is defined from the gravitational attraction between two masses. The gravitational force causes the less massive object to accelerate.
Forces and Newton’s Laws of Motion
Force Chapter 6. Force Any push or pull exerted on an object.
Chapter 4 Preview Objectives Force Force Diagrams
Chapter 4 Forces and the Laws of Motion. Chapter Objectives Define force Identify different classes of forces Free Body Diagrams Newton’s Laws of Motion.
Physics Chp4.
Chapter 4 Changes in Motion Objectives
What do you know about forces?
Free-body Diagrams To help us understand why something moves as it does (or why it remains at rest) it is helpful to draw a free-body diagram. The free-body.
Forces in One Dimension: Force and Motion 4.1
Force and Its Representation
Free Body Diagrams and Vector Diagrams.  Recap from ICT Package  Free Body Diagrams  Types of Component Forces  Vector Diagrams.
CHAPTER 4 The Laws of Motion Newton’s First Law: Newton’s First Law: An object at rest remains at rest and an object in motion continues in motion with.
Mechanics Topic 2.2 Forces and Dynamics. Forces and Free-body Diagrams To a physicist a force is recognised by the effect or effects that it produces.
Newton’s Laws of Motion
Newton’s Laws of Motion We have studied “kinematics”, or the description of motion. Now, we look at “dynamics”, the causes of motion.
Forces and Newton’s Laws of Motion. 4.1 The Concepts of Force and Mass A force is a push or a pull. Arrows are used to represent forces. The length of.
PAP Physics. Unit is the NEWTON(N) Is by definition a push or a pull Can exist during physical contact (Tension, Friction, Applied Force) Can exist with.
In order to change the motion Of an object, you must apply A force to it.
If something is moving, then something MUST be pushing on it
CHAPTER 4 FORCES IN 1-D FORCE Force is anything which causes a body to start moving when it is at rest, or stop when it is moving, or deflect once it.
Forces and Free Body Diagrams. Common Forces Gravity- attractive force between two objects that have mass. AKA Weight To calculate Weight: –Force of Gravity.
 Scalars are quantities that have magnitude only, such as › position › speed › time › mass  Vectors are quantities that have both magnitude and direction,
Chapter 4 Forces in One Dimension. 4.1 Force and Motion Force – A push or a pull exerted on an object. May cause a change in velocity:  Speed up  Slow.
Newton's Laws of Motion 1. Newton 1 st law of motion 2. Newton 3 rd law of motion 3. Newton 2 nd law of motion.
Force & Newton’s Laws of Motion. FORCE Act of pulling or pushing Act of pulling or pushing Vector quantity that causes an acceleration when unbalanced.
Forces & Motion “Trust the Force Luke” Forces Forces.
Physics 111: Mechanics Lecture 4
Force Diagrams And Types of Forces. Review Force = push or pull. Measured in Newtons. –1 lb = 4.45 N F net = ma a = F net / m Big force = big acceleration.
Chapter 5 THE LAWS OF MOTION. Force, net force : Force as that which causes an object to accelerate. The net force acting on an object is defined as.
Remember!!!! Force Vocabulary is due tomorrow
Newton’s 2nd Law of Motion. Forces A push or pull The cause of an acceleration Cause of a change in an object’s state of motion Cause objects to speed.
Dynamics If something is moving, then something MUST be pushing on it. Things don’t move all by themselves! Aristotle.
AP Physics C I.B Newton’s Laws of Motion. Note: the net force is the sum of the forces acting on an object, as well as ma.
Friction. Biblical Reference And they pulled him up with the ropes and lifted him out of the cistern. Jeremiah 38:13.
 Force: A push or a pull Describes why objects move Defined by Sir Isaac Newton.
Forces What is a Force? A force is any push or pull on an object A force does NOT always require contact –Gravity –Electrostatic –Magnetism.
Forces and the Laws of Motion
Force Chapter 6. Force Any push or pull exerted on an object.
Basic Information: Force: A push or pull on an object Forces can cause an object to: Speed up Slow down Change direction Basically, Forces can cause an.
Newton’s first and second laws Lecture 2 Pre-reading : KJF §4.3 and 4.4.
Forces and the Laws of Motion Chapter 4. Forces and the Laws of Motion 4.1 Changes in Motion –Forces are pushes or pullss can cause acceleration. are.
Laws of Motion Review.
 Write down everything you know about force. Things you may want to include: ◦ Definition ◦ Formula ◦ SI Units ◦ Examples.
Test #3 Notes Forces and the Laws of Motion Circular Motion and Gravitation Chapters 4 and 7.
Kinematics: how an object moves… what is its velocity, displacement, etc. Dynamics …why an object moves the way it does.
Forces and Newton’s Laws of Motion. A force is a push or a pull. Arrows are used to represent forces. The length of the arrow is proportional to the magnitude.
Weight = mass x acceleration due to gravity
Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 4 Force A force is a push or pull exerted on an object which.
FORCES IN ONE DIMENSION CHAPTER FOUR. FORCE Is a push or a pull exerted on an object. The object is called the system. Everything that surrounds the object.
Free Body Diagrams and Vector Diagrams.  Recap from ICT Package  Free Body Diagrams  Types of Component Forces.
FRICTION and Newton’s second law. The “Normal” Force, N When an object is pressed against a surface, the surface pushes back. (That’s Newton’s 3 rd Law)
Air Resistance and Free Body Diagrams
Newton’s Laws.
Forces Force- a push or pull
Force and Motion.
CHAPTER 4 FORCES IN 1-D.
Chapter 4 Newton’s Laws.
Forces and Newton’s Laws of Motion
Newton’s Laws.
Bell Ringer Socrative Quiz- Newton’s Laws Room: LEE346
Presentation transcript:

When released, the lift provides a net force of 6 N on a 2 kg balloon. If it started at rest, how fast will it be moving in 4.0 s? F net = 6 Nm = 2 kg v o = 0t = 4 s v f = ? v f = v o + at, so we need “a”. a = F net / m a = 6 N / 2 kg = 3 m/s 2 v f = m/s 2 x 4 s v f = 12 m/s F net = ma

Newton’s Three Laws 1.An object at rest remains at rest and an object in motion continues that motion unless acted upon by a net external force. 2.F net = mass x acceleration 3.For every force, there is an equal but opposite force.

A 1500 kg. car starts from rest and is moving at 10 m/s after 5.0 s. What was the net force on the car? m = 1500 kg V o = 0 V f = 10 m/s t = 5.0 s F net = ? F net = ma, so we need to find the acceleration. v f = v o + at a = ( v f – v o ) / t a = (10 m/s – 0) / 5 s = 2 m/s 2 F net = ma F net = 1500 kg x 2 m/s 2 F net = 3000 N F net = ma

Weight Weight, Wt. is the gravitational force acting on an object Your weight is determined by both your mass and the strength of the gravitational field (the acceleration due to gravity, “g”) Weight = mass x acceleration due to gravity Wt. = mg Since weight is a force, it is measured in Newtons, N Remember, “g” on Earth is 9.8 m/s 2

What is the weight of a 42 kg child on Earth? Wt. = mgm = 42 kg Wt. = 42 kg x 9.8 m/s 2 Wt. = N Weight = mg

What is the mass of a N car on Earth? Wt. = mg m = Wt. / g m = N / 9.8 m/s 2 m = kg Weight = mg

Remember, one Newton is not a very big force (about the same as a ¼ pound). So, your weight in Newtons is MUCH bigger than your weight in pounds! In fact, you would have to multiply your weight in pounds by 4.45 to get your weight in Newtons. How much do you weigh in Newton’s?

Even if you weigh 550 Newtons, You still wouldn’t be much of a Sumo Wrestler! (that’s only around 120 lbs)

“Net” Force F net = ma

More than one force can act on an object at the same time. For example, two people could push on a book at the same time. One person could push toward the left and the other could push toward the right. In this case the two forces would act against each other. Since Newton’s Law requires NET force, what is the NET force? 2 N towards the left If the book had a mass of ½ kg, what would be its acceleration? a = F net / m a = 2 N /.5 kg a = 4 m/s 2 (left) F net = ma

What if the opposing forces were equal? What is the net Force? What is the acceleration? If the forces are “balanced” forces, the net Force is zero and there will be NO acceleration! F net = ma

What if the forces were in the same direction? What is the net force? If the book had a mass of 2 kg, what is its acceleration? a = F net / m a = 14 N / 2 kg = 7 m/s 2 F net = ma

Free Body Diagrams Free-body diagrams are pictures used to show the relative magnitude and direction of all forces acting upon an object in a given situation. These diagrams are often used in physics. The length of the arrow in a free-body diagram sometimes is used to represent the magnitude (size) of the force. The direction of the arrow shows the direction that the force is acting. Each force arrow in the diagram is labeled to indicate the exact type of force. The object itself is either drawn as a box or squeezed down to a dot. The force arrows are always drawn pointing away from the center of the box. 3 kg 18N6N 15N

Examples of Free-Body Diagrams What are the unknown forces for the given net force?

Forces on an Airplane: if the forces are not “balanced”, there will be an acceleration! When Lift is larger than Weight, the plane will…. When Weight is larger than Lift, the plane will… When Thrust is larger than Drag, the plan will…. When Drag is larger than Thrust, the plane will…. When Thrust = Drag, the plane will… When Lift = Weight, the plane will….

We usually label forces as negative or positive. Forces upward are positive. Forces downward are negative. Forces to the right are positive. Forces to the left are negative

What is the net Force? - 6 N + 18 N = + 12 N What is the acceleration? a = F net / m 12 N / 3 kg = 4 m/s 2 3 kg 18N6N F net = ma

What is the net Force? - 6 N – 15 N + 18 N = - 3 N What is the acceleration? a = F net / m a = - 3 N / 3 kg = - 1 m/s 2 3 kg 18N6N 15N F net = ma

A parachute provides a lift force of 400 N on a parachutist that weighs 500 N. What is the net force on him? Use g = 10 m/s N What is his acceleration? a = F net / m What is his mass? Weight = mg a = -100 N / 50 kg a = - 2 m/s 2 Weight Parachute F net = ma

Tension Force Tension, T, is the force that cables, ropes, and strings pull with.

A child pulls up on a string that is holding 2 fish of total mass 5 kg. If he is providing a tension of 60 N, what is the net force on the fish? F net = Tension – Weight F net = 60 N – 50 N F net = 10 N What is the acceleration of the fish? a = F net / m a = 10 N / 5 kg a = 2 m/s 2 F net = ma

One child pulls up on a box with a force of 19 N. Another child pulls down on the box with a force of 5 N. What is the net Force? Hold on, there’s another force not drawn! The gravitational force of weight is also pulling down! Wt = mg, (g = 10 m/s 2 ) Wt = 2 kg x 10 m/s 2 = 20 N Draw the weight vector also! Now, what is the net Force? Net force = +19 N – 5 N – 20 N = Net Force = - 6 N What is the acceleration? a = Fnet / m = a = - 6 N / 2 kg a = -3 m/s 2 It will accelerate downward. 2 kg 19 N 5 N mg = 20 N F net = ma

, “sigma” is a Greek letter that is used to signify “the sum of” Quite often, in Newton’s 2 nd Law, we write  F = ma instead of F net = ma  F = ma

A child pulls a 5 kg bucket out of well with a rope. If the bucket accelerates upward at 1.2 m/s 2, what is the tension in the rope? m = 5 kg a = 1.2 m/s 2 T = ?  F = ma T – mg = ma T = ma + mg T = (5 kg x 1.2 m/s 2 ) + (5 kg x 9.8 m/s 2 ) T = 55 N T mg  F = ma

m = 2 kg a = 4 m/s 2 T = ?  F = ma T – mg = ma T = ma + mg T = (2 kg x 4 m/s 2 ) + (2 kg x 9.8 m/s 2 ) T = 27.6 N T mg A 2 kg cat grabs hold of a rope dangling from an alien spacecraft that is blasting off from Earth. What is the tension in the rope if the spacecraft accelerates straight upward at 4 m/s 2 ?  F = ma

Pre-AP: Now for some challenging problems…

A hockey player strikes the 0.5 kg puck with his hockey stick at an angle of 70 degrees. If he exerts a force of 60 N, with what acceleration will the puck slide across the frictionless ice?  F = ma F sin  = ma a = 

A boy pushing on a 15 kg lawnmower wants to produce an acceleration along the horizontal ground of 3 m/s 2. What force must he exert if his force is directed at an angle of 40 degrees measured from the horizontal? Required Force = mass x acceleration Force = 15 kg x 3 m/s 2 Horizontal Force = 45 N But…. Question: If the horizontal component of force is 45 N, what was the magnitude of the force the boy exerted at an angle of 40 degrees? Which trig function can be used to find the hypotenuse when the angle and adjacent side are known? Cos  = adj / hyp hyp = adj / cos  The boy’s force = N 45 N 40 o Force = ?  F = ma