Balanced and Unbalanced Forces


Duration: 60 minutes

Notes / Activity


Design a toy that exhibit types of forces

  • 3-PS2-1: Plan and conduct an investigation to provide evidence of the effects of balanced and unbalanced forces on the motion of an object. [Clarification Statement: Examples could include an unbalanced force on one side of a ball can make it start moving; and, balanced forces pushing on a box from both sides will not produce any motion at all.] [Assessment Boundary: Assessment is limited to one variable at a time: number, size, or direction of forces. Assessment does not include quantitative force size, only qualitative and relative. Assessment is limited to gravity being addressed as a force that pulls objects down.]

By the end of this lesson, the student should able to:

  • Design and develop a functional toy using a type of force. 

Lesson Plan

Lesson Introduction

Duration: 15 min

  • 2 foot piece of string or rope.
  • Tell students that they will play a game called “tug of war.” Pair off students and assign them partner A or B. Give them a ~2 foot piece of string or rope. Explain that they will each pull on the string and adjust the forces to test out what happens to the motion of their partner’s hand through the following scenarios. 
  • Emphasize safety and do this outside or in the gym. Get students to predict about which way each partner’s hand will move during each scenario.
  • Students observe balanced and unbalanced contact forces and non-contact forces through a variety of scenarios. 
  • Partner A pulls with the same amount of force as Partner B (neither partner will move) 
  • Partner A pulls with more force than Partner B (Partner B will move in the direction of Partner A)
  • Partner B pulls with more force than Partner A (Partner A will move in the direction of Partner B)
  •  While both partners are pulling, the rope is cut (they will both move) Organize the students into pairs and run through the scenarios. 
  • Elicit from students:


Were their predictions correct? Why or why not?


Elaborate and Evaluate

Duration: 50 min

  • Before this lesson, the teacher should have informed students that they will be designing a toy so that they can bring their materials to create the toy in class. 
  • Students will be working in groups to design their toy
  •  The toy would need to:
  • Exhibit one types of forces
  • Safe and functional (toy is able to work).
  • Get students to think of how they would want to create their toy and the materials that they would be using. 
  • They should bring along these materials and construct the toy in the classroom.
  • Walk around the classroom and evaluate students on how their toy exhibits different types of forces and listen out for students’ explanation on the effects of forces on their toys.
  • Get students to present to the class how their toys work.