Balanced & Unbalanced Forces Created by Kesler Science – More 5E lessons at KeslerScience.com Presented by Kesler Science

Essential Questions: What are balanced and unbalanced forces? How do unbalanced forces cause a change in position, direction, and speed of an object when acted upon by unbalanced forces?

Balanced and Unbalanced Forces A push or a pull that causes an object to stop, move, or change direction. Forces push downward toward the Earth’s center (gravity) or push upward on an object (normal or supporting force). Forces may or may not cause movement. Ex. 1 – A book pushes down on a table while the table pushes up on the book. Ex. 2 – A car accelerates(changes speed and direction)causing motion. © KeslerScience.com

Forces Template Quick Action – Forces INB Template Cut out the Balanced, Unbalanced, Net Force template. Fold along the dashed lines. Glue it to your journal along the skinny tab. Define each term. © KeslerScience.com

Balanced and Unbalanced Forces Two forces equal in size and acting in opposite directions on an object. The object stays still or continues to move at the same (constant) speed and in the same direction. Students understand the concept of balanced forces being at rest, but struggle to grasp the concept that forces are balanced if the object continues moving at the same speed and in the same direction. © KeslerScience.com

Balanced Forces Examples Balanced and Unbalanced Forces Balanced Forces Examples At rest At rest At rest At a constant speed and same direction At a constant speed and same direction © KeslerScience.com

Unbalanced Forces Balanced and Unbalanced Forces Always cause a Two forces that are unequal in size and opposite in direction. Always cause a change in motion in one of these areas: position direction speed © KeslerScience.com

Unbalanced Forces Examples Balanced and Unbalanced Forces Unbalanced Forces Examples Horse #2 is stronger 20N Moves Left 10N The student exerting the strongest force will determine the direction of movement. Changing directions © KeslerScience.com

Which way will they move? Balanced and Unbalanced Forces Net Force  The overall forces acting on an object. Measured in Newtons (N) Net Force1N 3N 2N Which way will they move? © KeslerScience.com

Quick Action – Demonstrate Forces Choose a partner for this activity. The teacher will number off the pairs. Even numbered pairs will come up with an example of a balanced force, which they will present to the class. 3. Odd numbered pairs will come up with an example of a unbalanced force, which they will present to the class. (Use examples of changing either position, speed or direction) © KeslerScience.com

Quick Action – Balanced or Unbalanced Template Cut out the template Fold the flaps away from the side that says “Glue this side down” Glue it to your journal on the hexagon side that says “Glue this side down” Answer “balanced” or “unbalanced” under each flap. © KeslerScience.com

Balanced and Unbalanced Forces How do unbalanced forces cause a change in position of an object? A skier is at the top of a hill (balanced force). Another skier bumps him (unbalanced force) causing him to fall down. This unbalanced forced caused his position to change.   © KeslerScience.com

Balanced and Unbalanced Forces How do unbalanced forces cause a change in direction of an object? A skier is at the top of a hill (balanced force). Then then the skier decides to point her skis down the hill and push off (unbalanced force). This unbalanced force causes her a change in direction.   © KeslerScience.com

Balanced and Unbalanced Forces How do unbalanced forces cause a change in speed of an object? A skier is at the top of a hill (balanced force) at the beginning of a race. As he flies down the mountain (unbalanced force) he picks up speed. This unbalanced force causes him a change in speed.   © KeslerScience.com

Check for Understanding Can you… 1. Describe balanced and unbalanced forces? 2. Identify and describe how unbalanced forces cause a change in position, direction, and speed of an object when acted upon by unbalanced forces? Clear up any confusion and answer questions. © KeslerScience.com