## LESSONS: Forces

###### The majority of lesson ideas below require minimal resources other than the smartphone, and are relevant to introductory physics in high school and college. However, creative individuals are using smartphone science in more complex ways, with drones, engineering kits, and much more. Follow us on Twitter @PhysicsToolbox and see our Publications page for additional content. ###### Forces on an Inclined Plane

What is the relationship between the INCLINE ANGLE and FORCES on an object placed on an inclined plane?

Try This

Using the G-Force and Orientation tools, determine how the components of the forces acting on an object change as the angle of incline changes,

Related Resources ###### Newton's Laws with an Atwood's Machine

What is the relationship between MASS, NET FORCE, and ACCELERATION for an object?

Try This

The relationship between mass, net force, and acceleration of an object is frequently displayed using an Atwood's Machine (two masses suspended over a pulley system) or a modified Atwood's Machine (one mass suspended over a pulley system, pulling on a frictionless object over a horizontal surface).

Using the Accelerometer tool, place the mobile device in a plastic bag and suspend it from a traditional or modified Atwood's Machine composed of pulleys and string. Using known masses and mass of the mobile device using a balance, determine the net force on each object. Use the data to determine the acceleration. Perform experiments in which acceleration is measured resulting from changes in mass and net force on the system.

Challenge Yourself

• Create a graph of Net Force vs. Acceleration, and derive a mathematical expression for this relationship.

• Creat a graph of Mass vs. Acceleration, and derive a mathematical expression for this relationship.

• If there are any constants in the mathematical expressions above, explain their significance.

• Combine the two expressions into a single expression.

• Using the expression and a new system of given mass, estimate the expected acceleration. Compare to the actual acceleration observed using the smartphone data.

Related Resources ###### Newton's Laws with an Elevator Ride

How does the NORMAL FORCE on my body change during an elevator ride?

Try This

Use the Accelerometer tool and place the mobile device flat on the floor of an elevator during a ride up and a ride down. Use a body scale to determine your mass. For each part of the elevator ride (accelerating up, moving up at constant velocity, accelerating down on the way up, etc.), draw a quantitative force diagram for your body by calculating the net force, normal force, and weight acting on you.

Challenge Yourself

• Complete the worksheet listed below in "Resources."

• How would this experience be different if you were on another planet, or if you weighed more?

Related Resources ###### Impulse in Collisions

How well do different materials decrease the FORCE OF IMPACT between two objects?

Try This

Using the Accelerometer tool, determine which bumper materials decrease the average force of impact on a cart rolling down an inclined plane into a barrier.

Challenge Yourself

• Which material most decreased the force? Why?

• Would it be beneficial for the bumper and the barrier to have material properties that caused the cart to bounce? Why or why not?

Related Resources