FORCES Ch 8.1
What is FORCE? Recall force is a push or a pull on an object ELASTIC FORCE Recall force is a push or a pull on an object A force can Move an object Change the movement of an object Change the shape of an object FRICTION FORCE TENSION FORCE
Types of Forces We can group forces into TWO main categories: (1) Contact Forces Object is touched (2) Action-at-a-distance Forces No touching
CONTACT FORCES Contact Force Definition Tension force A force experienced by a wire or a rope when it’s pulled Friction force A force that is caused by two surfaces rubbing together Elastic force A force is exerted on a spring-like object and returns to its original shape.
Is FORCE Involved???
Is FORCE Involved???
Is FORCE Involved???
Is FORCE Involved???
Is FORCE Involved???
Is FORCE Involved???
Is FORCE Involved???
Bigger objects that are close together = greater force Gravitational Force 2 objects that have MASS are attracted by gravitational force! Bigger objects that are close together = greater force We don’t feel gravitational force between ourselves and other objects on Earth because the Earth is so HUGE (it’s gravitational influence is stronger).
Electrostatic Force This is static electricity – caused by CHARGED particles! Same charges -> repel Opposite charges -> attract
Magnetic Force These forces act on metals (ex: Iron, Nickel...) Magnets have a field that surrounds them and can exert pushing and pulling forces. The Earth itself has a natural magnet deep in its core!
Freeze High Five What are contact forces? Give 3 examples What are action at a distance forces? Give 3 examples
Mass and Weight Jupiter Mass is the amount of MATTER in an object Mass is measured in kilograms (kg), use a balance to measure Weight is different from mass Weight is the amount of force on an object due to gravity Gravity is not the same everywhere... 117 kg 50 kg 8 kg Jupiter Earth Moon
Measuring Force We measure force in a unit called the newton (N) 1 N is about the amount of force you would need to hold up an apple 1 N Sir Isaac Newton – handsome fellow NOTE: Weight is a force so it should be measured in N. We often use kg by habit.
Freeze! “High 5” Reading Checks What units are used to measure a force? What effect does friction have on the motion of an object? What is the difference between mass and weight?
Forces and Motion Who wins in a tug-of-war? The stronger side! We can think of forces in this way! Forces that are equal and opposite are balanced.
Forces and Motion Unbalanced forces causes movement 20 N Net Force Friction 2 N
Unbalanced forces Four things that could happen to an object if an unbalanced force acts on an object: Change of speed Change of direction It could stop It start the movement of an object