1. Unit 4 Lesson 2 Balanced and Unbalanced Forces
Copyright © Houghton Mifflin Harcourt Publishing Company

2. A Force, of Course! What is a force?
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 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

3. How do forces act on objects?
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

4. How do forces act on objects?
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

5. In the Balance What is net force?
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

6. How is net force calculated?
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

7. Get Moving! How do balanced and unbalanced forces affect motion?
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

8. How do balanced and unbalanced forces affect motion?
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

9. Push and Pull How is force calculated?
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