Module 1 Motion Speed Velocity Acceleration What is

Module 1 Motion

Speed, Velocity, & Acceleration • What is Speed? – Scalar Quantity (only have magnitude) – How fast something is moving – Distance traveled over time – No direction • Average speed is not instantaneous speed

Speed, Velocity, & Acceleration • Distance • Overall amount traveled

Speed, Velocity, & Acceleration • Units of speed are derived units of distance over time • Speed (meters/second) = distance (meters) /time (seconds)

Let’s Practice!!!! • In a skateboarding marathon, the winner covered 435 km in 36. 75 h. What was the winner’s average speed? • Florence Griffith Joyner set a world record by running 200 m 21. 34 s. What was her average speed? • An airplane is traveling at 400 mi/hr. It touches down at an airport 2000 mi away. How long was the plane airborne?

Speed, Velocity, & Acceleration • d/t graphs – X-axis = time – Y-axis = distance (position) • Speed on distance-time graphs – Think slope of line: check it out • Analyzing distance vs time graphs • ***Figure 7 in book***

Speed, Velocity, & Acceleration What was the object’s speed at 2 s? What was the object’s speed at 5 s? How would describe the motion of this car? What might you predict the next plot point to be?

Speed, Velocity, & Acceleration What was the object’s speed at 2 s? The object stopped during this time frame. When did this happen? Explain how you know. What happened between 9. 8 s and 12 s? How do you know?

Speed, Velocity, & Acceleration How is this graph different? How would you describe the motion of this object? Can we still calculate speed? ? How? ?

Speed, Velocity, & Acceleration

Speed, Velocity, & Acceleration • Frame of Reference • Motion is Relative to Frame of Reference • You observe how other objects move by comparing to that frame of reference

Speed, Velocity, & Acceleration • Velocity – Vector Quantity (magnitude and direction) – Speed and direction • Speed and Velocity are not the same

Speed, Velocity, & Acceleration • Velocity – Vector Quantity (magnitude and direction) – Speed and direction • Speed and Velocity are not the same Speed velocity Scalar quantity Vector quantity How fast object is going with Speed and direction respect to frame of reference Ex. 50 miles per hour, North

Let’s Practice!!!! • A cart starting from rest travels a distance of 3. 6 meters northward in 1. 8 seconds. What is the average velocity? • A car drives from Tallahassee to Orlando. The distance is 830 km and the drive takes 7. 3 hrs. What is the velocity of the car?

Speed, Velocity, & Acceleration • Rate at which velocity changes – Speeding up (positive) – Slowing down (negative) – Changing direction

Speed, Velocity, & Acceleration • Calculating Acceleration

Let’s Practice !!!! • A roller coaster speeds up going down a hill from 0 m/s to 11 m/s at the bottom of the hill. If this occurs in 3 seconds, what is the acceleration of the roller coaster? • A cheetah is running at a velocity of 14 m/s and slows to tackle a wildebeast to 2 m/s. If the chase takes 4. 2 seconds, what is the cheetah’s acceleration?

Speed, Velocity, & Acceleration • v/t graphs – X-axis = time – Y-axis = speed – Analyzing speedtime graphs – Think slope of line: – ***Figure 16 in book***

Speed, Velocity, & Acceleration Find the acceleration between 2 -5 seconds. How would you describe this object’s motion? What would the next plot point would be? How do you know?

Speed, Velocity, & Acceleration Find the acceleration between 2 -4 seconds. Find the acceleration between 7 -9 seconds. What is happening between 4 -7 seconds, How do you know? ?

Speed, Velocity, & Acceleration

The Laws of Motion • Force – A push or a pull – Measured in newtons

The Laws of Motion • Balanced and Unbalanced Forces

The Laws of Motion • Drawing and Interpreting Force Diagrams

The Laws of Motion • Net Force • Rules for Adding Forces – Add forces in the same direction. – Subtract forces in opposite directions – Forces not in the same directions or in opposite directions cannot be directly added together.

The Laws of Motion • Friction • Force that works against the motion of an object

The Laws of Motion • Newton’s 1 st Law – An object at rest will stay at rest and an object in motion will stay in motion, unless an unbalanced force acts on it. – Break It Down: INERTIA – Things want to keep doing what they are doing – Inertia is directly related to mass.

The Laws of Motion • Newton’s 2 nd Law – Acceleration of an object is directly affected by the net force acting on it, and inversely by the mass of the object

The Laws of Motion • Newton’s 2 nd Law – Force (N) = mass (kg) x acceleration (m/s 2)

Let’s Practice!!!! • With what force will a car hit a tree if the car has a mass of 3, 000 kg and it is accelerating at a rate of 2 m/s 2? • If a helicopter’s mass is 4, 500 kg and the net force on it is 18, 000 N upward, what is it’s acceleration?

The Laws of Motion • Newton’s 3 rd Law – For every action (force applied) there is an equal and opposite reaction (resulting force)

The Laws of Motion • Momentum – Mass of an object times its velocity – A vector quantity (magnitude and direction) – Momentum = mass x velocity

The Laws of Motion • Conservation of Momentum – Momentum remains constant for objects interacting with one another in a system

Let’s Practice!!!!

Let’s Practice!!!!

Let’s Practice!!!!

The Laws of Motion • Angular Momentum – Deals with rotational motion – Is a product of mass and velocity – Depends on the distribution of mass – Angular mass (moment of inertia)

Forces in Action • 4 basic Forces – Gravititational – Electromagnetism – Strong nuclear force – Weak nuclear force

Forces in Action • Gravitational – Force of attraction between two objects – Depends on mass and distance – Weakest of the four forces

Forces in Action • Gravity and Weight – Measures the force of gravity on mass – Weight and Mass are different things

Forces in Action • Falling for Gravity – Force of air friction between falling object and air particles – All objects regardless of mass, experience the same acceleration when in free fall

Forces in Action • Electromagnetic Forces – Forces occur when electric field interacts with electrically charged particles – Opposite charges attract, like charges repel

Forces in Action • Strong Nuclear Forces – Work at the atomic level – Strong Forces – Force that holds the nucleus of atom together – Strongest of the 4 forces, short range

Forces in Action • Weak Nuclear Forces – Work at the atomic level – Weak Forces – Force responsible for particle decay (radioactivity)

Forces in Action Force Description of the force Particles Range of the Relative strength that force of the force experienc e the force Gravity Attraction between All particles Infinity objects with mass Weakest of the 4 forces Electromagnetism Attraction or Electrically repulsion between charged electrically charged particles Infinity Second strongest of the 4 forces Strong nuclear Hold’s the atoms nucleus together Atoms and subatomic particles Short range Strongest of the 4 forces Weak nuclear Governs nuclear decay and radioactivity Atoms and subatomic particles Short range Second weakest of the 4 forces

Energy • Energy – Ability to change or move matter – Exists in many forms • Potential – – Nuclear Elastic Chemical gravitational • Kinetic – – Electrical Radiant Thermal Mechanical

Energy

Energy • Energy Conversions • Law of Conservation of Energy – Energy cannot be created or destroyed, just converted from on form to another

Energy • Kinetic Energy – energy of motion – depends on mass and speed • Kinetic Energy = ½ mass x speed (KE = ½ m v 2) KE (J) = ½ m (kg) X v (m/s)2

Energy • What is the kinetic energy of a 136. 4 kg elephant moving at 34 m/s? • What is the kinetic energy of a 22. 7 kg boy on his 45. 5 kg bike rolling down a hill 25 meters high at 7. 21 m/s? • Determine the kinetic energy of a 1000 -kg roller coaster car that is moving with a speed of 20. 0 m/s.

Energy • • Potential Energy • • stored energy(elastic, chemical, gravitational) • Gravitational Potential Energy = mass x gravity x height • GPE (J) = m (kg) g (N/kg) h (m)

Energy • What is the potential energy of a hammer that weighs 25 N that is sitting on top of a ladder 5 meters high? • What is the potential energy of a golf ball that weighs 3. 2 kg that is resting on top of a 1. 2 m high lab table?

Energy

Energy

• Systems Energy – The container or entity • Isolated system (neither energy or matter exchange) • Closed system (energy can enter or leave, matter cannot) • Open system (energy and matter exchanged freely)

Work & Power • Energy is the ability to do work • Force exerted over a distance • Force must be in the same direction as the distance

Work or Not Work • A book falls off a table and free falls to the ground. • A waiter carries a tray full of meals above his head by one arm straight across the room at constant speed. • A rocket accelerates through space. • A teacher applies a force to a wall and becomes exhausted.

Work & Power • Calculating work • Work = force x distance • Work and force are directly related

Let’s Practice !!!! • How much work is needed to push an object that weighs 350 N a distance of 4 meters? • A dancer lifts a 400 N ballerina overhead a distance of 1. 4 m. How much work is done? • How much work is done by an applied force to lift a 15 -Newton block 3. 0 meters? • How much work is done on the wall by a person pushing on the wall with 5600 N of force?

Work & Power • Negative Work • A force acts on an object to stop or slow motion • Force acts in direction opposite of the motion

Work & Power • Machine – • Types of machines – Simple machines – Compound machines • Two or more simple machines

Work & Power • How are machines useful? • Increase speed • Change direction of force • Increase the force • Mechanical advantage – MA = output force (N) input force (N)

Let’s Practice !!!! • To pull a weed out of a garden, you can apply a force of 50 N to the shovel. The shovel applies a force of 600 N to the weed. What is the mechanical advantage of the shovel? • To lift a block on a movable pulley, you can apply a force of 50 N to a rope. The rope applies a force of 700 N to the block. What is the mechanical advantage of the rope?

Work & Power • Efficiency – – Efficiency (%) = output work (J) input work (J) – Machines can be made more efficient by reducing friction – All machines are less than 100% efficient

Work & Power • You do 222 J of work pushing a box up a ramp. If the ramp does 200 J of work, what is the efficiency of the ramp? • Find the efficiency of a machine that does 800 J of work if the input work is 2, 000 J.

Work & Power • • Power Rate at which work is done Can be more work or work done faster Hand saw versus power saw

Work & Power • • Calculating power Power (watts) = work(joules)/time (seconds) Power and time inversely related Power and work directly related

Let’s Practice !!!! • A light bulb uses 300 J of energy in 4 seconds. How much power does the light bulb require? • What is the power of an electric toothbrush if it can do 755. 8 joulles of work in 75 seconds? • An athlete is using the row machine in the gym. She does 3245 joulles of work on the oars in 72 seconds. What is her power output?

Work & Power • Power = work /time = force x distance • Power = force x distance /time • Power = force x velocity • Power is related directly to velocity