# PH.5 b, d-f - Motion and Gravity

The student will investigate and understand the interrelationships among mass, distance, force, and time through mathematical and experimental processes. Key concepts include

b)  uniform circular motion;

d)  Newton’s laws of motion;

e)  gravitation; and

f)  planetary motion.

Bloom's Levels:  Analyze; Understand

### BIG IDEAS

• I can explain why roller coasters don't fall off the track when they go upside down.
• I can explain why I get "thrown" to one side in the car on a sharp turn.
• I can explain why two objects falling from the same height will hit the ground at the same time.
• I can explain why the Earth stays in orbit.

### UNDERSTANDING THE STANDARD

The concepts developed in this standard include the following:

• Newton’s three laws of motion are the basis for understanding the mechanical universe.
• In a uniform vertical gravitational field with negligible air resistance, horizontal and vertical components of the motion of a projectile are independent of one another with constant horizontal velocity and constant vertical acceleration.
• An object moving along a circular path with a constant speed experiences an acceleration directed toward the center of the circle.
• The force that causes an object to move in a circular path is directed centripetally, toward the center of the circle.  The object’s inertia is sometimes falsely characterized as a centrifugal or outward-directed force.
• Weight is the gravitational force acting on a body.
• Newton’s Law of Universal Gravitation can be used to determine the force between objects separated by a known distance, and describes the force that determines the motion of celestial objects. The total force on a body can be represented as a vector sum of constituent forces.

### ESSENTIALS

In order to meet this standard, it is expected that students will

b) distinguish between centripetal and centrifugal force.

describe the forces involved in circular motion.

d) solve problems involving force (F), mass (m), and acceleration (a).

solve problems involving multiple forces, using free-body diagrams.

e-f) solve problems using Newton’s Law of Universal Gravitation.

### KEY VOCABULARY

Updated: Dec 01, 2017