Unit 4 Lesson 2 Balanced and Unbalanced Forces

Unit 4 Lesson 2 Balanced and Unbalanced Forces A Force, of Course! What is a force? • A force is a measurable push or pull that acts on an object. • The SI unit of measurement for a force is a newton. • A spring scale is often used to measure weight since it can measure the force of a pull in newtons. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 4 Lesson 2 Balanced and Unbalanced Forces How do forces act on objects? • Like velocity and acceleration, force is a vector quantity. • Force is a quantity that has both strength and direction. • Arrows can be used to show the direction and strength of a force, with the relative length of the arrow representing the force’s strength. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 4 Lesson 2 Balanced and Unbalanced Forces How do forces act on objects? • Applied forces involve direct contact with an object. • Friction is a force that opposes the motion between two surfaces that are in direct contact. • Other forces, like gravity and magnetism, can act on object at a distance. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 4 Lesson 2 Balanced and Unbalanced Forces In the Balance What is net force? • The net force is the combination of all forces acting on an object. • Balanced forces act in opposite directions and the motion of the object does not change. • Unbalanced forces do not cancel one another out, and they affect an object’s motion. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 4 Lesson 2 Balanced and Unbalanced Forces How is net force calculated? • When two forces act in opposite directions, the smaller force can be subtracted from the larger force to determine the net force. • When forces are balanced, the net force is zero. • When two forces act in the same direction, they can be added together to determine the net force. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 4 Lesson 2 Balanced and Unbalanced Forces Get Moving! How do balanced and unbalanced forces affect motion? • Velocity is the speed of an object in a particular direction. • Acceleration is the rate at which velocity changes. • An object accelerates if it changes speed, direction, or both. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 4 Lesson 2 Balanced and Unbalanced Forces How do balanced and unbalanced forces affect motion? • When forces are balanced, an object will have constant velocity and zero acceleration. • When forces are unbalanced, an object will accelerate and show a change in velocity. • Some objects, such as a spinning carousel, can have constantly changing velocity. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 4 Lesson 2 Balanced and Unbalanced Forces Push and Pull How is force calculated? • If you know the mass and acceleration of an object, you can calculate the force that caused the acceleration. • Units of force are newtons, mass units are kilograms, and acceleration units are meters per seconds squared. • Force equals mass times acceleration. Copyright © Houghton Mifflin Harcourt Publishing Company