BELLWORK 10/5/17 -Get out textbook pages 335-347 -NB: Write “IN” and today’s date. A boulder is resting a the top of a hill, then suddenly begins moving down the side of the hill. Why did the boulder move? An unbalanced force acted on the boulder and caused it to move.
TYPE OF Forces Contact vs. Noncontact © Copyright 2015. All rights reserved. www.cpalms.org
Force: A push or Pull? Pushing and Pulling are both Applied Forces Pushing in opposite directions (towards each other) cancel each other out Pulling (and force of gravity and ropes Pushing and Pulling are both Applied Forces
“Through” contact vs. non-contact forceS A force that can cause or change motion of an object in direct contact (touching). Force that results when the two objects are at a distance from each other, yet are able to exert a push or pull. Create a foldable to demonstrate both types of forces with examples and drawings of each BOTH FORCES TRANSMIT ENERGY – I.E. FRICTION TRANSFORMS TO HEAT ENERGY WIND PUSHES A WINDMILL BLADE- KINETIC ENERGY OF MOVING AIR TRANSFERRED TO BLADES MAKING THEM TURN Contact Force Examples: Applied Force Friction Normal Force Non-Contact Force Examples: Gravitational Force Electrical Force Magnetic Force © Copyright 2015. All rights reserved. www.cpalms.org
Contact Forces Applied Force: A force of push or pull Friction: A force that slows motion when a moving object touches another object. Normal Force: The force that doesn’t cause a change in motion. Examples of each? pushing a door open, pulling a rope. Friction – ice skates on ice or rubbing hands together to create heat energy as kinetic energy in hands is transformed the support force exerted upon an object that is in contact with another stable object. For example, if a book is resting upon a surface, then the surface is exerting an upward force upon the book in order to support the weight of the book.
Contact Forces Cyclist movement Friction Normal force = 10N Image credits: Cyclist Laura Brown by Flickr user Flowizm, https://www.flickr.com/photos/flowizm/9715876836/sizes/l (CC BY-NC-SA 2.0) Military skydiver by Pixabay user skeeze, https://pixabay.com/en/parachute-skydiving-parachuting-713654/ (CC0 Public Domain) Friction Normal force = 10N Weight = 10N
NON-Contact Forces Magnetic Force: Force where some metals attract or repel magnets Electrical Force: Force of electrical charges. Gravitational Force: The force of attraction between any two objects in the universe. All objects have gravitational force. The mass of an object and its distance determines the strength of its gravitational force. © Copyright 2015. All rights reserved. www.cpalms.org
Non-Contact Forces Gravity Electrical transfers energy to heat and light energy Gravity transfers potential (hanging apple to falling apple) to kinetic energy
Classify the Forces A foot kicking a soccer ball An apple falling off a tree A paper clip sliding towards a magnet A bat striking a baseball Two magnets pushing apart from one another The moon orbiting the Earth A compass needle turning North A hand pushing an object Shoes rubbing against the floor Have students specify contact or non- contact as well as specific type of force. For example: A foot kicking a soccer ball is a contact force: applied force. Answers: 1. Applied 2. Gravity 3. Magnetic 4. Applied 5. Magnetic 6. Gravity 7. Magnetic 8. Applied 9. Friction © Copyright 2015. All rights reserved. www.cpalms.org
C F What type of force? A B D E
Before the ball is kicked. When the ball is kicked *Before the ball is kicked? *When the ball is kicked? *Once the ball is in motion? *throughout? What type of force? Normal Applied Friction Gravity
what forces are exerted during tug of war? “Out” During tug of war the rope is pulled (applied, friction (slowing on one side or the other, of the rope, friction and gravity) During tug of war the rope is pulled (applied, friction (slowing on one side or the other, of the rope, friction and gravity)