motion, forces, and simple machines unit week 35 directions 1.prepare your desk for science. science...
TRANSCRIPT
Motion, Forces, and Simple Machines Unit
Week 35Directions1.Prepare your desk for science.
• Science notebook
2.Use voice level 2 (conversation) to discuss this question: “What is a force? What do you know about forces?”
Targets & Warm Up
Targets:• Students will identify contact forces that affect
motion.• Students will demonstrate and describe the way
things move and change motion.
Warm Up: What is a force? What do you know about forces?
Table of Contents
Date Title Page5-28-15 Contact Forces 87
Once you are finished with the Table of Contents, go to page 87 and add the title and date to the top of the page.
Force
Force• Any push or pull that can make an object
move or make a moving object move faster, slow down, stop, or change direction
Force
• Can change both the position and motion of an object
• The size of the change depends on the strength of the push or pull
Contact Forces: Applied Force
What are some other examples of applied forces that you have seen or experienced? Make sure that the force is between two objects!
Contact Forces: Friction
2. Friction• A force that acts when two surfaces rub together• It can slow or stop moving objects or keep
objects from starting to move
Contact Forces: Friction
• The amount of friction between two surfaces depends on:– The object’s surface– How hard the objects press together
Contact Forces: Friction
A. The smooth base of the skis slides smoothly on the snow.
B. The boy on the grass is having difficulty sliding, because the grass is not smooth and his shoes are getting stuck in the grass.
Contact Forces: Friction
• If you push a box of feathers along the floor, it is easy to push.
• If you push a box of books along the floor, it presses against the floor with more force. This causes more friction. The box is harder to push.
Isaac Newton’s Laws of Motion
An object at rest tends to stay at rest, and an object in motion tends to stay in motion, with the same direction and speed.
The only reason an object will begin to move, change direction, or change speed is because of a force.
Try this…
• Use contact forces to make the ball move• Use contact forces to make the ball…
–Change speed–Change direction–Stop
Try this…
Make the item moveMake the item change speed
Make the item change direction
Make the item stop
Other Types of Contact Forces• Air resistance force: The air
resistance force acts upon objects as they travel through the air.
• Spring force: The spring force is the force exerted by a compressed or stretched spring upon any object which is attached to it.
Other Types of Contact Forces
• Tension force: The tension force is transmitted through a string, rope, or cable.
• Normal (support) force:– If an object is resting upon a
table then the table is applying force upon the object.
– If a person leans against a wall, the wall pushes on the person.
Targets (Revisited)
• Students will identify contact forces that affect motion.
• Students will demonstrate and describe the way things move and change motion.