**Core Ideas:**

- For any pair of interacting objects, the force exerted by the first object on the second object is equal in strength to the force that the second object exerts on the first, but in the opposite direction (Newton’s third law).
- The motion of an object is determined by the sum of the forces acting on it; if the total force on the object is not zero, its motion will change. The greater the mass of the object, the greater the force needed to achieve the same change in motion. For any given object, a larger force causes a larger change in motion.
- All positions of objects and the directions of forces and motions must be described in an arbitrarily chosen reference frame and arbitrarily chosen units of size. In order to share information with other people, these choices must also be shared.

**Learning Activities:**

*Do Now*– Get out your science notebook and open to page 85. Read the procedure for the investigation- Forced to Accelerate.*Introduce the STEM Bridge Structural Design Project**Investigation*– Forced to Accelerate- How is acceleration related to force?- Follow the procedure and record your data in the data table on page 85 in your science notebook.*Textbook Assignment*– Read pages 51-54. Define key word on page 51. Do the Math Sample Problem and Math Practice on page 53. Answer all questions 1-4 on page 54.