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Forces
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Force Forces are measured in Newtons (N)
One Newton is the amount of force required to give a 1-kg mass an acceleration of 1 m/s2.
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Forces Change Motion Forces usually act in pairs
Forces affect how objects move. They may cause motion; they may also slow, stop, or change the direction of motion of an object that is already moving Forces act in a particular direction Forces usually cannot be seen, but their effects can
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Strength and Direction of Forces
ARROWS can be used to show forces. The of an arrow shows the of the force. The that the arrow points shows the direction in which the The stronger the force the the arrow. LENGTH STRENGTH DIRECTION FORCE WAS APPLIED LONGER
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Force: A push or Pull Contact Force Non-Contact Force
A force that can cause or change motion of an object by touching it. Motors and gears operate through contact forces. Force that results when the two objects are not in physical contact with each other, yet are able to exert a push or pull. Contact Force Examples: Friction Normal Force Air Resistance Applied Force Non-Contact Force Examples: Gravitational Force Electrical Force Magnetic Force
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Contact Forces Applied Force: A force typical push or pull, pushing a door open, pulling a rope. Friction: Happens when two objects rub against each other. Friction opposes motion. Normal Force: The normal force is 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. Air Resistance: The air resistance is a type of frictional force that acts upon objects as they travel through the air.
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Contact Forces Normal Force= 10N
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NON-Contact Forces Magnetic Force: A kind of non contact force, materials such as iron, nickel, cobalt and other magnets just need to be near the magnet to be attracted or repelled. Electric Force: Noncontact 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.
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Gravity
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Forces usually act in pairs
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Balanced and Unbalanced Forces
Forces occur in pairs and can be either balanced or unbalanced. Balanced forces do not cause a change in motion. They are equal in size and opposite in direction. Unbalanced forces always cause a change in motion. They are not equal and opposite. The final force and its direction are called a resultant, the difference is the net force. A net force causes an acceleration. An unbalanced force is needed to change an object’s direction
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Is There a Net Force? Combine your prior understanding of acceleration with your newly acquired knowledge that a net force causes an acceleration to determine whether or not a net force exists in the following situations: YES NO YES NO YES YES
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Drawing Vectors to Show Force
A force can be shown with a vector. A vector is a line with an arrow. It begins with a dot. A dot shows where the force begins The length of the arrow shows the amount of force The arrows shows the direction Resultant vectors can be shown as a result of opposite or combined forces
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Combining Forces - Unbalanced
Forces acting on an object that combine and form a net force that is not zero. Unbalanced forces cause an object to move. Forces moving in the same direction are Forces moving in the opposite direction are ADDED SUBTRACTED
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HMM…. Can you see the unbalanced force here?
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Combining Forces – Balanced Forces
Forces acting on an object that combine and form a net force of ZERO. NO change in motion.
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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.
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