Balanced and Unbalanced Forces

• Lesson 2 introduces balanced and unbalanced forces.
• The lesson also covers friction and its role in forces.
• It falls under Unit 10, Understanding Forces.

Learning Outcomes

• Learners should be able to identify and describe everyday situations that demonstrate balanced forces.
• Examples of balanced forces: a box resting on an inclined plane, a man standing still, or an object moving with constant velocity.
• Learners should be able to identify and describe everyday situations that demonstrate unbalanced forces.
• Examples of unbalanced forces: a freely falling fruit or an accelerating car.
• Learners should be able to draw a free-body diagram to represent the relative magnitude and direction of forces involving balanced and unbalanced forces.
• Learners should be able to identify that when forces are not balanced, they can cause changes in the object's speed or direction of motion.
• Learners should be able to understand the concept of friction and its role in balanced and unbalanced forces.

Learning Targets

• Differentiate between balanced and unbalanced forces.
• Learn to create free-body diagrams to represent forces.
• Understand the effects of unbalanced forces on motion.
• Understand the role of friction in balanced and unbalanced forces.

Introduction to Forces

• Forces and friction shape the motion of objects and whether they remain still.
• Understanding forces helps to explain balance, motion, and the critical role of friction, including in the Philippines.
• The concepts of balanced and unbalanced forces, as well as friction, are evident in competitive activities like tug-of-war.

Warm-Up Activity: Tug-of-War Challenge

• Materials needed for this activity are a rope, a marker to mark the ground, a stopwatch, and a measuring tape.
• The procedure involves:
• Marking a line on the ground as the starting point.
• Dividing students into groups, each taking an end of the rope, with the middle aligned with the ground marker.
• Starting on "Go," with each team pulling as hard as possible.
• Recording the time taken and distance pulled for each team.

Reflect and Discuss (Tug-of-War)

• Reason about why some teams may pull harder than others, considering forces.
• Explain the effect on the participants' feet on their ability to pull, relating it to friction.
• Suggest an example of a situation where balanced forces are at play, similar to tug-of-war at a standstill.
• In tug-of-war, balanced forces occur when both teams exert equal force.
• Unbalanced forces occur when one team exerts more force, pulling the other team.

Balanced and Unbalanced Forces

• When two or more forces are equal, these forces are balanced.
• Balanced forces result in equilibrium, where objects stay in position (at rest) without motion.
• Equilibrium can be disturbed with unbalanced forces.
• Unbalanced forces occur when magnitude of one of the forces exceeds the other.
• The thrust from rocket engines pushed the world's first rocket to reach space upward, fighting against Earth's gravity.

Friction

• Friction is a force that opposes the motion of one surface as it moves across another.
• Friction can either help balance other forces or make them unbalanced, depending on the situation.

Free-Body Diagram

• A free-body diagram (FBD) is a graphical representation that depicts all external forces acting upon a single object, with each force illustrated as an arrow.
• Three essential characteristics of FBDs are:
• The arrow is labeled according to the type of force.
• It points in the direction the force is applied.
• The length of the arrow reflects the relative magnitude of the force, with longer arrows indicating stronger forces and shorter arrows for weaker ones.
• Assumptions in FBD include:
• The object is rigid.
• The mass of the object is constant.
• The object is not spinning.

Commonly Encountered Types of Forces in FBD

• Fnorm - Normal Force
• Ftens - Tension Force
• Fgrav - Gravitational Force
• Ffric - Frictional Force
• Fapp - Applied Force
• When drawing a free-body diagram the questions to answer include:
• What are the forces acting on the object?
• Where is the direction of the force?
• Are the forces acting on the object balanced or unbalanced?
• Net force can be calculated through calculation.

Key Points

• Forces can cause objects to start or stop moving, speed up, slow down, or change direction.
• Balanced forces act on an object in opposite directions and are equal in size, causing no change in the object's motion.
• Unbalanced forces occur when the net force on an object is not zero, resulting in a change in the object's motion.
• Friction is a force that opposes the motion of an object, and it can be either beneficial or a hindrance, depending on the situation.
• A free-body diagram (FBD) is a graphical representation used to visualize forces, helping to determine whether they are balanced or unbalanced.

Explore balanced and unbalanced forces with real-world examples. Learn to identify these forces in everyday situations and understand how they affect motion. Includes free-body diagrams to represent force magnitudes and directions.