### Linear Motion - Reading: Chapter 2, Page 660-661

### Key Terms for Unit

### AccelerationAverage timeElapsed TimePosition

### FreefallInstantaneous speedRateDistance

### RelativeSpeed VelocityDisplacement

### Chapter 2 Objectives:

When you have completed Chapter 2, you should be able to:

- ... recognize that a rate is a quantity divided by a time interval.
- ... distinguish between average speed and instantaneous speed, between speed and velocity.
- ... calculate the average speed of an object (given displacement and time interval) and recognize appropriate speed units.
- ... discuss what is meant by the statement " motion is relative".
- ... identify when an object's velocity is changing and when acceleration occurs.
- ... differentiate between velocity and acceleration.
- ... calculate the acceleration of an object (given change in velocity and time interval) and recognize appropriate acceleration units.
- ... solve numerical problems involving objects having velocity and acceleration.
- ... state the acceleration of an object in free fall near the earth's surface in metric and "English" units.
- ... recognize that the acceleration of an object in free fall is constant.
- ... solve problems involving objects in freefall
- ... discuss the effect of air resistance on falling objects in terms of distance traveled and velocity.

Massachusetts Frameworks – standards in bold are addressed in this unit.

**1. Motion and Forces**

## Broad Concept: Newton’s laws of motion and gravitation describe and predict the motion of most objects.

1.1**Compare and contrast vector quantities (such as, displacement, velocity, acceleration, force, and linear momentum) and scalar quantities (such as, distance, speed, energy, mass, and work). **

1.2**Distinguish between displacement, distance, velocity, speed, and acceleration. Solve problems involving displacement, distance, velocity, speed, and constant acceleration.**

1.3**Create and interpret graphs of 1-dimensional motion, such as position vs. time, distance vs. time, speed vs. time, velocity vs. time, and acceleration vs. time where acceleration is constant.**

1.4Interpret and apply Newton’s three laws of motion.

1.5Use a free-body force diagram to show forces acting on a system consisting of a pair of interacting objects. For a diagram with only co-linear forces, determine the net force acting on a system and between the objects.

1.6Distinguish qualitatively between static and kinetic friction, and describe their effects on the motion of objects.

1.7Describe Newton’s law of universal gravitation in terms of the attraction between two objects, their masses, and the distance between them.

1.8Describe conceptually the forces involved in circular motion.

Variable / Symbol / Unit / SignTime / t / Second, s / Can only be +

Position / x / Meter, m / Can be + or –

Displacement / x / Meter, m / Can be + or –

Distance / x or d / Meter, m / Can only be +

Velocity / v = x/t / m/s / Can be + or -

Acceleration / a= v/t / m/s/s or m/s2 / Can be + or -

Basic Formulas:

Velocity: v = x/tacceleration: a = v/t

x = vit + ½ at2For 0 initial velocity: x = 1/2at2