PHYSICS - LEVER CLASSES #3

CLASS 3 LEVER






CLASS ONE LEVER




CLASS TWO LEVER

PHYSICS - SIMPLE MACHINES - ACTIVITIES #2

SIMPLE MACHINES

LEVERS

PHYSICS - SIMPLE MACHINES REVIEW

Add to your notes from class discussion as needed.
Complete quiz - turn in score once you make 100%

STUDY JAMS - SIMPLE MACHINES

SIMPLE MACHINE - MATCHING

Simple Machines

More educational videos on Simple Machines at NeoK12.com  

 Simple machines are tools that make work easier.  They have few or no moving parts.  These machines use energy to work.  

Compound machines have two or more simple machines working together to make work easier.

In science, work is defined as a force acting on an object to move it across a distance. 

• Pushing, pulling, and lifting are common forms of work. Furniture movers do work when they move boxes. Gardeners do work when they pull weeds. Children do work when they go up and down on a see-saw. Machines make their work easier. The furniture movers use a ramp to slide boxes into a truck. The gardeners use a hand shovel to help break through the weeds. The children use a see-saw to go up and down. The ramp, the shovel, and the see-saw are simple machines.

Lever
Inclined Plane
Wheel and Axle
Screw
Wedge
Pulley

SIMPLE MACHINES - QUIZ

PHYSICS - LEVERS REVIEW

Remember:  

There are 3 kinds of Levers.  Every kind of Lever has:

• a balance point (fulcrum)
• a point where the weight is
• a point where force is applied

Add these study questions in your notes as well as the following information on Levers.

LEVERS

Questions For Study

1. Why is energy needed?
Energy is needed to do work.

2. How do scientists define “work”?
Work occurs when a force moves an object.

3. What is the difference between class 1, class 2, and class 3 levers?
A class-1 lever has the fulcrum located somewhere between the effort and the load. With this kind of lever, the direction of force is changes. Effort applied downward moves the load up. Effort applied upward moves the load down.



A class-2 lever has its fulcrum at one end of a lever arm. The load is between the fulcrum and the effort. With this kind of lever, the direction of effort is not changed. Pushing up on the class-2 lever arm pushes up on the load. Pushing down on the lever arm pushes down on the load. To gain a mechanical advantage, the load is places closer to the fulcrum than to the effort. The class-2 lever always reduces effort.



In a class-3 lever, the fulcrum is at one end, and the effort is applied between the fulcrum and the load. With this kind of lever, the direction of effort is not changed. The load moves in the same direction as the effort. The gain offered by a class-3 lever is one of distance.


4. Explain why a simple machine makes work easier to do but does not save energy.Most simple machines do not save energy. They distribute the force needed to do work over a longer distance.

Generally, simple machines can help us in two ways. We can apply less effort over a greater distance, or we can apply more effort over a shorter distance. Simple machines provide a gain in effort or a gain in distance. In addition, some simple machines change the direction of effort.

5. How does a lever or pulley give you mechanical advantage?Sometimes we may want to lift, push, or pull an objects, or we may need to break or cut them. Some of these jobs require a lot of force. When we use simple machines, we gain a mechanical advantage by increasing the amount of force we can bring to bear on an object.

6. What is friction? When is it necessary to reduce friction?Friction is a force that slows down or stops motion. There is friction when two parts of a machine rub against each other.

One way to reduce friction is by covering surfaces that rub together with grease or oil. Another way is by using wheels.

7. What is the difference between a fixed and a movable pulley?A fixed pulley can change the direction of your force. You pull down on one end of the rope. The load is pulled up by the other end. It takes the same force to lift a load with a fixed pulley as it does without a fixed pulley.

A movable pulley does not change the direction of your force. Like a lever, a movable pulley lets you use less force to lift a load. But you must pull the rope a longer distance than the load moves. The smaller force needed to lift a load with a movable pulley is used over a longer distance. So a movable pulley does not save energy.

8. Where in real life can you find levers and pulleys?

• Examples of class-1 levers are: a seesaw, claw hammer, crowbar, scissors, pliers, and tin snips.

• Examples of class-2 levers are: a wheelbarrow, paper cutter, door, nutcracker, garlic press, bellows, and a bottle opener.

• Examples of class-3 levers are: a fishing pole, hammer, baseball bat, hockey stick, golf club, tennis racket, shovel, pitchfork, hoe, broom, tweezers, ice tongs, and your arms and legs.

• Pulleys are used to lift items from one level to another. 
• Pulleys can be fixed or movable or combinations of both.
•  Pulleys are used in block and tackles, large cranes, chain hoists, and hydraulic systems.

9.  TYPES OF LEVERS:

Levers are simple machines that have a rigid arm around a fixed point or fulcrum. 

Force is transferred from one part of the arm to another. 

• The input (effort) force is multiplied or redirected into anoutput (resistance) force. 
• Levers are divided into three different classes. 
• A first-class lever has the fulcrum between the input and output forces. 

A Type 1 Lever.

 In a Type 1 Lever, the pivot (fulcrum)  is between the effort and the load. In  an off-center type one lever (like a  pliers), the load is larger than the  effort, but is moved through a smaller  distance.

Examples of common tools (and other items) that use a 

Type 1 lever include:

Item		Number of Class 1 Levers Used
see-saw		a single class 1 lever
hammer's claws		a single class 1 lever
scissors		2 class 1 levers
pliers		2 class 1 levers

A SECOND-CLASS LEVER has the output force between the fulcrum and the input force. 

A Type 2 Lever.

In a Type 2 Lever, the load is between the pivot (fulcrum) and the effort.

Examples of common tools that use a type 2 lever include:

Item		Number of Class 2 Levers Used
stapler		a single class 2 lever
bottle opener		a single class 2 lever
wheelbarrow		a single class 2 lever
nail clippers		Two class 2 levers
nut cracker		Two class 2 levers

The third-class lever has the input force between the fulcrum and the output force. 

A Type 3 Lever.

 In a Type 3 Lever, the effort is  between the pivot (fulcrum) and the  load.

Examples of common tools that use a type 3 lever include:

Item		Number of Class 3 Levers Used
fishing rod		a single class 3 lever
tweezers		Two class 3 levers
tongs		Two class 3 levers

Different types of LEVERS into their appropriate classes.

 LABEL THE DIAGRAM

PHYSICS - VECTORS #3

VECTORS

Vector Basics

Force is one of many things that are vectors. 

What the heck is a vector? 

• Can you hold it? No. 
• Can you watch it? No. 
• Does it do anything? Well, not really. 

A vector is a numerical value in a specific direction, and is used in both math and physics. 
The force vector describes a specific amount of force and its direction. 

• You need both value and direction to have a vector. Both. Very important. Scientists refer to the two values as direction and magnitude (size). 
• The alternative to a vector is a scalar. Scalars have values, but no direction is needed. Temperature, mass, and energy are examples of scalars. 

When you see vectors drawn in physics, they are drawn as arrows. 

• The direction of the arrow is the direction of the vector
• the length of the arrow depends on the magnitude (size) of the vector. 

Real World Vectors

Imagine a situation where you're in a boat or a plane, and you need to plot a course. There aren't streets or signs along the way. You will need to plan your navigation on a map. You know where you're starting and where you want to be. The problem is how to get there. Now it's time to use a couple of vectors. 
Draw the vector between the two points and start on your way. As you move along your course, you will probably swerve a bit off course because of wind or water currents. Just go back to the map, find your current location, and plot a new vector that will take you to your destination. Captains use vectors (they know the speed and direction) to plot their courses. 

Combining Vectors

You know how to add and subtract. Scientists often use vectors to represent situations graphically. When they have many vectors working at once, they draw all the vectors on a piece of paper and put them end to end. When all of the vectors are on paper, they can take the starting and ending points to figure out the answer. The final line they draw (from the start point to the end point) is called the Resultant vector. If you don't like to draw lines, you could always use geometry and trigonometry to solve the problems. It's up to you. Unlike normal adding of numbers, adding vectors can give you different results, depending on the direction of the vectors.

PHYSICS - FORCES #2

Forces of Nature

Forces are a big part of physics. Physicists devote a lot of time to the study of forces that are found everywhere in the universe. 

The forces could be big, such as the pull of a star on a planet. The forces could also be very small, such as the pull of a nucleus on an electron. Forces are acting everywhere in the universe at all times. 

Examples of Force

If you were a ball sitting on a field and someone kicked you, a force would have acted on you. As a result, you would go bouncing down the field. There are often many forces at work. Physicists might not study them all at the same time, but even if you were standing in one place, you would have many forces acting on you. Those forces would include gravity, the force of air particles hitting your body from all directions (as well as from wind), and the force being exerted by the ground (called the normal force). 



Let's look at the forces acting on that soccer ball before you kicked it. As it sat there, the force of gravity was keeping it on the ground, while the ground pushed upward, supporting the ball. On a molecular level, the surface of the ball was holding itself together as the gas inside of the ball tried to escape. There may have also been small forces trying to push it as the wind blew. Those forces were too small to get it rolling, but they were there. And you never know what was under the ball. Maybe an insect was stuck under the ball trying to push it up. That's another force to consider. 



If there is more than one force acting on an object, the forces can be added up if they act in the same direction, or subtracted if they act in opposition. Scientists measure forces in units called Newtons. 

• When you start doing physics problems in class, you may read that the force applied to the soccer ball (from the kick) could be equal to 12 Newtons. 

A Formula of Force

There is one totally important formula when it comes to forces, F = ma.    That's all there is, but everything revolves around that formula.

"F" is the total (net) force
"m" is the object's mass
"a" is the acceleration that occurs

As a sentence,

"The net force applied to the object equals the mass of the object multiplied by the amount of its acceleration." 

The net force acting on the soccer ball is equal to the mass of the soccer ball multiplied by its change in velocity each second (its acceleration). Do you remember the wind gently blowing on the soccer ball? The force acting on the ball was very small because the mass of air was very small. Small masses generally exert small forces, which generally result in small accelerations (changes in motion). 

Forces and Vectors

We cover the details of vectors on another page. A vector can be used to represent any force. A force vector describes a specific amount of force that is applied in a specific direction. If you kick that soccer ball with the same force, but in different directions, and you get different results... 

The Force Rule

• Force is affected in 2 ways:

1. An object of greater mass has a greater force (e.g. An adult baseballer will hit the ball further than a child)
2. An object with greater acceleration has a greater force (e.g. A faster karate expert can strike with greater force than a slower person)

• Force Rule
  
  

Force (newtons)	= Mass (kilograms) × Acceleration (meter per second-squared)
F	= m × m/s2
F	= m × a
F	= ma

• Force Rule Example
  Question: Daring Darius, the human cannonball whose mass is 100 kg, is accelerated from a cannon at 5 m/s². What force was used?

Answer:	F	= ma
		= m × a
		= 100 × 5
		= 500 N (newtons)