Motion & Newtons LawsState Correlation 2c & 2f
What is MOTION?All matter is in constant motionMotion is any change in positionRelative Motion is used to recognize a change in position by using a point of referenceAn object changes positions if it moves relative to a reference point
Measuring MotionDistance is the total length of the route an object travels when it movesDisplacement includes distance from the starting point to the stopping point and the direction traveledEx. 40m 30m Distance = 40m Displacement = 40m east 40mDistance = 70mDisplacement = 50m northeastDistance = 140mDisplacement = 0m
Distance and Displacement
SpeedSpeed is the distance traveled divided by the time taken to travel the distanceFormula: Speed = distance time (S=D/T)SI Unit: meters per second (m/s)Ex. In the 100m dash the fastest runner finished in 10s. S= 100m/10s= 10m/s3 Types of SpeedAverage speed is found by dividing the total distance by the total time taken to reach that distanceSpeeds can vary from instant to instantEx. Walking in a crowded hallwayInstantaneous Speed is the speed of an object at a particular moment (clap sporadically) . . .. Constant Speed is when an object is moving at a steady rate throughout the entire distance (clap a steady beat) . . . .
Practice ProblemCalculate the Average Speed. Round to the nearest 0.1m/sA swimmer swam 100m in 56s.
Graphing MotionMotion can be graphed on a distance-time graph Time on the horizontal axis Distance on the vertical axis
The steeper the line on a distance-time graph, the greater the speedA horizontal line means no change in position, which makes the speed zero at anytime on the graph
Which student is moving fastest?Which student has no motion?Example Graph
Time in seconds
Distance in meters
Distance Verses Time
TimeStudent AStudent BStudent C
VelocityVelocity is the speed of an object and the direction of its motion.Unit is same as speed, but includes direction10km/h east
Example: A hiker needs to know how far away the camp is & in what direction to determine the necessary velocity to get back to camp before nightfall
AccelerationAcceleration occurs when an object changes its motion (velocity changes)Speed up - 50m/h to 60m/h (positive)Slow down 45m/h to 40m/h (negative)Acceleration is in the opposite direction of the motionChange in direction north to eastBasket ball thrown from the free-throw line
Can you think of examples of situations that have positive or negative acceleration?
Newtons Laws of MotionState correlation 2f
What is a Force?Force is defined as a push or a pullEx. Pushing a grocery cart or pulling a wagon
Net force is the combination of all forces acting on an object at the same time.Ex. Identify all the forces acting on a paper clip, sitting on a table, near a magnet.
Balanced verses UnbalanceBalanced forces occur when two or more forces exerted on an object cancel each other out causing no change in motion (no acceleration)Ex. Lean back to back with a partner with no motion or hold a book in your hand very still
Unbalanced forces occur when the combined forces acting on an object do not cancel each other out causing a change in motion (acceleration)Ex. Push a chair with wheels or when someone wins tug-a-war
Decide if the situation is Balanced or UnbalancedPush a box till it moves Pedal a bike at a constant speedApply brakes to a bike in order to pop a wheelie Push a car that never movesTwo people push a box in opposite directions causing the box to go nowhereTwo people push a box in opposite directions causing the box to slide slightly to the right.UBUBBU
Newtons 1st Law of Motion 2 partsAn object will remain at rest until an unbalanced force is applied to the objectEx. Skateboard pushed in motion
An object in motion will remain in motion at a constant rate until an unbalanced force is applied to the objectEx. Moon moves in a consistent patternKnown as the law of inertiaInertia is the tendency of an object to resist change in its motionEx. Applying breaks in a car and your body goes forward
Newtons First Law of Motion
FrictionFriction is a force that resists sliding between two touching surfaces or through air or water.Friction slows down an objects motion.Friction produces heat and wears on objects
FrictionRubbing your hands together, you can feel a force between your hands.
FrictionFriction is always present when two surfaces of two objects slide past each other.
Static FrictionKeeps an object at rest from moving on a surface when force is applied to the object.
Sliding FrictionSliding friction occurs when two surfaces slide past each other.
Rolling FrictionA car or truck stuck in the mud spins its wheels but doesnt move. Rolling friction makes a wheel roll forward or backward. A car stuck in the mud doesnt have enough rolling friction to keep the wheels from slipping.
Air ResistanceWhen molecules in air collide with the forward-moving surface of an object, slowing its motion. Resistance is less for a narrow, pointed object than for a large, flat object.
Newtons 2nd LawNewtons second law of motion connects force, acceleration, and mass an object acted on by a force will accelerate in the direction of the forceacceleration equals net force divided by mass.Ex. An empty skateboard verses a person standing on a skateboard: Which one will you have to push harder to go the same distance?Formula: (a = fnet m) or (fnet = m x a)Forces are measured in Newtons (N)1N = 1kg x 1m/s2
Newtons 2nd Law of Motion
Newtons 2nd Law of Motion
Practice Newtons 2nd lawSuppose you pull a 10kg sled so that the net force on the sled is 5N. What is the acceleration of the sled?A = 5N 10kg = 0.5m/s2You throw a baseball with a mass of 10kg so it has an acceleration of 40m/s2. How much force did you exert on the baseball?Answer: 400NMaking a connection: Explain the connection between motion, 1st law, & 2nd law.
Newtons 3rd LawNewtons third law of motion states that forces always act in equal but opposite pairs called action/reaction forcesfor every action there is an equal and opposite reaction.Bounce a ball on the ground or playing poolAction-reaction forces are always the same size but are in opposite directions and act on different objects.When the mass of one object is considerably larger than the mass of another object, the action-reaction force is not noticeable. When you push a wall or walk on the earth.
Newtons 3rd Law of Motion
Newtons 3rd Law of Motion
Action/Reaction ForcesWhen one object exerts a force on another object the 2nd object exerts the same size force on the 1st objectForces act on different objects, so they do not cancel each other out
Action/ Reaction ExamplesUnderline the objectActionWings push air down & back
Hands push water back
Foot pushes down and back on earth
Rocket engine pushed gas molecules downwardReactionAir pushes wings up and forward
Water pushes swimmer forward
Earth pushes foot up &forward
Gas molecules push rocket upWhy does the reaction not always appear to be the same?The greater the mass the greater the inertia
Which law?Using an oar to move a canoePushing a swing with more force to move your big brother than you did with your little sisterA rock is sitting on a hill until you push it causing it to rollQuiz3rd1st2nd
*Hw wksht p27 ch21 sec1 1-8only*Show a balance with the same items in both pans & then more of the item in one pan than the other*Have students create their own example problem and trade with a partner to solve.*Have students underline the different objects the forces act on