THINK LIKE A SCIENTIST

WorkMotionEnergy7th Grade ScienceMs. DeFreeseSeptember 25, 2012

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EnergyThe ability to do work and cause change.

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Law of Conservation of EnergyEnergy cannot be created or destroyed

Energy may change form, but the total amount remains the same

Kinds of EnergyKineticEnergy of motion (moving energy)

PotentialEnergy at rest (stored energy)

ForceA push or pull that could cause a change in an objects motion

Balanced or UnbalancedBalanced forces = no change in motionOften referred to as equilibrium

Unbalanced forces = change in motion

Measuring ForceForce can be measured using a spring scale

Measured in newtons (N)

Force and WorkForce can produce work if acted over a distance.

Work can be calculated by w = F x dForce can be calculated by F = w d

GravityA force or attraction that exist between any two masses.

Gravity depends on the MASS of objects and DISTANCE between them

GREATER MASS or SMALLER DISTANCE = STRONGER GRAVITY

MassThe amount of matter in something

Measured in GRAMS or KILOGRAMS

Never changes . . . Remains constant

WeightFORCE that GRAVITY exerts (has) on a mass

Measured in newtons (N)

Changes depending on relationship between mass and gravity

Measuring WeightExample: You weigh 120 pounds on EarthGravity on the moon is 1/6 of that on Earth

Your WEIGHT on the moon = 1/6 of your weight on Earth (on moon you would weigh 20 pounds)

Your MASS on the moon = your mass on the EarthWhat you are made of (mass) does not change it remains constant

AssignmentComplete Understanding Forces Concept Map

When complete, glue this in your science journal

We will grade this at the beginning of class tomorrow.

What is work?Work is done when a force causes an object to move in the same direction that the force is applied.

The object must move.

Units of MeasureForce is measured in Newtons (N)

Distance is measured in meters (m)

Work is measured in Joules (J)1 J = 1 N/m

Is it work?A Joule is the amount of work done, BUT if work is to be done, then the object has to be moved in the same direction as the force.

If you spent hour pushing on a parked car, you were tired, hot and sweaty, you may feel like you have worked, but if the car never moved then you did NO work.

ExampleA force of 10 Newtons, that moves an object 3 meters, does 30 n-m of work. W = F x D (W = FD) W = 10N x 3m 30 N/m = 10N x 3m W = 30 Newton-metersA Newton-meter is the same thing as a joule

Work or No Work?

Even though he is exerting force, nothing is being moved a distance, therefore no work is being done.

Work or No Work?

Force is being exerted and an object (fire truck) is being moved.

MotionThe process of moving from one place to another

3 kinds: Straight(walking)Circular(Bicycle Wheel) Vibration (Guitar String)

Sir Issac Newton & the Laws of Motion

He was born in England on December 25, 1643. He was born the same year that Galileo died. He lived for 85 years. Isaac Newton was raised by his grandmother. He attended Free Grammar School and then went on to Trinity College Cambridge. Newton worked his way through college. While at college he became interested in math, physics, and astronomy. Newton received both a bachelors and masters degree. While Newton was in college he was writing his ideas in a journal. Newton had new ideas about motion, which he called his three laws of motion. He also had ideas about gravity, the diffraction of light, and forces. Newton's ideas were so good that Queen Anne knighted him in 1705. His accomplishments laid the foundations for modern science and revolutionized the world. Sir Isaac Newton died in 1727.

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Newtons First Law of MotionAn object at rest will remain at rest unless acted on by an unbalanced force. An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force

What does this mean?

What it meansThere is a natural tendency of objects to keep on doing what they're doing. In the absence of an unbalanced force, an object in motion will maintain this state of motion.

What is the motion in this picture?

What is the unbalanced force in this picture?

What happened to the skater in this picture? Example 1

Example 2This law is the same reason why you should always wear your seat belt.

Newtons Second Law of MotionAcceleration is produced when a force acts on a mass. The greater the mass (of the object being accelerated) the greater the amount of force needed (to accelerate the object).

What does this mean?

What it meansheavier objects require more force to move the same distance as lighter objects.

Newtons Third Law of MotionFor every action there is an equal and opposite re-action.

What it meanswhenever an object pushes another object it gets pushed back in the opposite direction equally hard.

Example 2The rocket's action is to push down on the ground with the force of its powerful engines, and the reaction is that the ground pushes the rocket upwards with an equal force.

Reminder: Work isWork: remember that for work to be done the object must move in the same direction as the force.

Work (W) = Force (F) x distance (d)W = Fd

Balanced or Unbalanced Forces

Example questions - balanced and unbalanced forces

Formula 1 car accelerating from the starting gridA cyclist brakingA satellite orbiting the Earth at constant speedA person resting in an armchairA taxi travelling at a constant speed on straight road.

Work Force DistanceUse the formula for Work to fill in the table glue the table in your journal

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