Force & Motion

Standard SPS8. Students will determine relationships among force, mass, and motion. *a. Calculate velocity and acceleration. b. Apply Newton’s three laws to everyday situations by explaining the following: Inertia Relationship between force, mass and acceleration Equal and opposite forces c. Relate falling objects to gravitational force d. Explain the difference in mass and weight. e. Calculate amounts of work and mechanical advantage using simple machines.  

Essential Question What is the difference between speed and velocity? What is acceleration? How do you calculate velocity and acceleration?

Essential Question What does a flat line mean on a speed/velocity graph? What does a flat line mean on an acceleration graph?

Essential Question What does the slope of a distance time graph represent? What does the slope of a velocity/time graph represent?

Learning Target YOU should understand the difference between speed and velocity and how to calculate it YOU should understand what acceleration is and how to calculate it

Learning Target YOU should understand how to determine if a graph is a speed/velocity or acceleration graph.

An object is in motion if it changes position relative to a reference point. Stationary objects—such as a tree, a sign, or a building—make good reference points. The passenger can use a tree as a reference point to decide if the train is moving. A tree makes a good reference point because it is stationary from the passenger’s point of view.

Describing Motion Whether or not an object is in motion depends on the reference point you choose.

Distance When an object moves, it goes from point A to point B – that is the DISTANCE it traveled. (SI unit is the meter) Distance is how much ground an object has covered during its motion. B A

Displacement Knowing how far something moves is not sufficient. You must also know in what direction the object moved. Displacement is how far the object is from its starting point. You use the shortest distance (in this case the hy hypotenuse).

Displacement can be 0 ! REMEMBER THIS!!! For example, a runner starts at a certain point and runs completely around the track. If the finish line is at the original starting point, the displacement is 0 even though the runner actually ran a distance of 400 meters.

SPEED Describes how fast an object is moving.

Average Speed distance Average Speed = time

Speed Calculating Speed: If you know the distance an object travels in a certain amount of time, you can calculate the speed of the object. What is instantaneous speed? Instantaneous speed is the velocity of an object at a certain time. Speed = Distance/time Average speed = Total distance Total time

Velocity The speed of an object in a certain direction 55 mph = speed 55 mph East = velocity

Velocity Formula Velocity = displacement time For the formula, displacement = distance velocity = speed

d Velocity V = t V = velocity (meters/second) d = distance (meters) speed of an object in a certain direction. V = velocity (meters/second) d = distance (meters) t = time (seconds)

Velocity speed of an object in a certain direction. seconds 3 1 2

Speed=? Velocity=? Total time= 4 seconds B 20 meters 12 meters

Numerator 5 12 Denominator

Acceleration

Acceleration is how quickly velocity changes over time. 3 1 2   Speed 3 1 2 Meters/second

Acceleration Acceleration is a change in speed or direction. If a car is travelling at a constant speed of 55 mph, it does have a speed but the acceleration is 0 because the speed is not changing. If the car is going around a curve at a constant speed of 25 mph, even though the speed is constant, the car is accelerating because it is changing direction.  

(Vfinal - Vinitial) ___________ A = time Acceleration how quickly velocity changes over time. (Vfinal - Vinitial) ___________ A = time

The graph below relates speed and time of four cars (1, 2, 3, and 4) traveling along a straight highway. Which two cars move with zero acceleration? 1 and 4 2 and 3 1 and 2 3 and 4

Scalar Vector SPEED VELOCITY A measurement that does NOT require a direction. _________ is Scalar. SPEED Vector A measurement that DOES require a direction. _________ is a Vector. VELOCITY

What must happen to an object in order to accelerate it? A net force must be applied. Some weight must be removed. Its frictional coefficient must be reduced. It must contain momentum.

Which of these describes the object with the largest acceleration ? An object with a small change in velocity over a small change in time An object with a small change in velocity over a large change in time An object with a large change in velocity over a small change in time An object with a large change in velocity over a large change in time

Which of the following is certain to change as a ball accelerates? mass of the ball inertia of the ball velocity of the ball force acting on the ball

Gravitational Magnetic Forces of Nature Gravitational Magnetic

Mass and Inertia The universe consists of matter in motion

The greater the mass the harder it is to move. And . . . the harder it is to stop moving.

Lower mass objects are easier to move . . .and to stop moving.

NEWTON’s Laws 1st Law of Motion : An object remains at a   An object remains at a in a ,until a net force acts on it. constant speed straight path

An object will remain at a constant speed (unless disturbed). NEWTON’s 1st Law of Motion is the law of Inertia ih ner shah An object will remain at a constant speed (unless disturbed).

the force of a moving body. momentum the force of a moving body. ___________ the mass times velocity of an object p = m • v Momentum = mass x velocity (Kgrams) (meters/second)

p = m • v Momentum = mass x velocity Higher mass higher momentum Higher velocity higher momentum p = m • v

Momentum points in the direction of motion. includes velocity. So, it has direction. Momentum points in the direction of motion.

Conservation of momentum When objects collide, all of the momentum goes somewhere.

Conservation of momentum When objects collide, all of the momentum goes somewhere.

When objects collide, all of the momentum goes somewhere. Conservation of momentum When objects collide, all of the momentum goes somewhere.

When objects collide, all of the momentum goes somewhere. Conservation of momentum When objects collide, all of the momentum goes somewhere.

NEWTON’s 2nd Law of Motion :   An object that has a force acting on it will change its speed (accelerate).

f = m•a NEWTON’s 2nd Law of Motion : f = net force (newtons)   f = m•a force = mass • acceleration f = net force (newtons) m = mass (Kilograms) a = acceleration (meters/second2)

f = m•a NEWTON’s 2nd Law of Motion : mass of the club   f = m•a mass of the club acceleration of the club force of the club

Conservation of energy NEWTON’s 3rd Law of Motion:   Conservation of energy For every action there is an equal and opposite reaction.

NEWTON’s 3rd Law of Motion: For every action, there is   For every action, there is an equal and opposite reaction.

NEWTON’s 3rd Law of Motion: For every action, there is   For every action, there is an equal and opposite reaction.

A car is traveling down a hill A car is traveling down a hill. Which of the following will affect the amount of energy the car has? how long the car is the time of day how much the car weighs the color of the car

Oliver the dog doesn't want to walk in the rain Oliver the dog doesn't want to walk in the rain. He can make his owner pull harder on the leash to get him out the door by sitting on the vinyl floor. sitting on the tile floor. sitting on the carpeted floor. sitting on the wood floor.

terminal velocity gravity will accelerate an object until air resistance (friction) does not allow it to go any faster. gravity air resistance

In the absence of air resistance, which of these objects will fall at the fastest rate when dropped? the ball with a mass of 75 kg the ball with a mass of 25 kg the ball with a mass of 10 kg They all fall at the same rate.

Pressure is the amount of force exerted over a certain area. Pressure = Force Area

Pressure = Force (newtons) Area (m2) 1 Pascal = 1 Newton/meter2

Gravitational force Gravity

All objects in the universe are attracted to each other by the force of effort. friction. gravity. inertia.

Four pairs of objects have the masses shown below Four pairs of objects have the masses shown below. If the objects in each pair are the same distance apart, the gravitational force between the objects in which pair is greatest? 1 kilogram and 1 kilogram 1 kilogram and 2 kilograms 2 kilograms and 1 kilogram 2 kilograms and 2 kilograms

As an astronaut travels from Earth to a space station orbiting Earth, what happens to her mass and weight? Her mass decreases, but her weight remains the same. Her mass increases as her weight decreases. Her mass remains the same, but her weight decreases. Her mass decreases and her weight also decreases.

Which hill would you slide down the fastest? hill A hill B hill C It would take the same time to slide down all of the hills.

50 39.2 29.4 19.6 9.8 Projectile Motion 3 1 2 Velocity (m/s) seconds forward downward 50 39.2 29.4 19.6 9.8 seconds 3 1 2

Projectile Motion Velocity (m/s) forward downward 48 47 46 50 49 39.2 29.4 19.6 9.8 seconds 3 1 2

Simple Machines Pulley Wheel & Axle Lever Inclined plane Screw Wedge Gear

Lever action 2 meters 1 meter Force= ? Force=13 N

Mechanical Advantage= final distance starting distance 9 meters 3 meters

Mechanical Advantage= distance distance 8 meters 2 meters

Which of the following is often used as a lever? file nail saw crowbar

The Wedge

calculating mechanical Advantage A 200 pound man lifts a rock weighing 800 pounds by standing on the end of a lever. How much mechanical advantage did the lever provide ?              calculating mechanical Advantage M.A. = 800 Kg/200 Kg = 4

If you wuz ‘n a Merry-go-round & yuz let go, Which wayz wud yu go?

Satellites stay in place as they orbit because of . . . the repeated firing of rocket boosters. the gravitational pull of Earth. a narrow path through the vacuum of space. solar panels generating energy to hold them in place

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