- Review velocity and acceleration and their interpretation from graphs

- Distinguish mass from weight and define force

- Investigate the the Law of Inertia

TODAY’S OUTCOMES:FORCE, MOTION AND ENERGY

*Suppose we were on a bus, and had a carpenter’s level which we put on a level spot on the floor. What would be bubble do

>when the bus starts moving?

>when the bus is traveling down Euclid Avenue at constant speed?

>when the bus stops?

>when the bus makes a right turn?

The bubble would shift to the front.

The bubble would be centered, since there is no acceleration.

The bubble would shift toward the right.

The bubble would shift to the rear.

The bubble shifts toward the direction of acceleration.

> At some airports there is a subway that will take you from one terminal to the next. Here is a graph that shows the position of the subway car as it goes from Terminal A to Terminal B, a distance of 200 meters.

a) What is the maximum speed of this subway car?

Steepest part of the distance vs. time plot isthe maximum speed

speed is give by the slope

120 m

8 secHighest speed = slope of steepest part = 120 m / 8 sec = 15 m/sec

b) Estimate the acceleration of the subway car as it starts to move.

6 sec

It takes 6 seconds for the car to reach maximumspeed;

Acceleration = change in velocity / time interval = 15 m/sec / 6 sec = 2.5 m/sec/sec

= 2.5 m/sec2

2) If there’s a curve, there’s an acceleration.

1) If you can draw a straight line on the plot, speed is (nearly) constant over that interval.

blue = (almost)constant speed

red =acceleration

3) Curved “valley” is forward (positive) acceleration, a curved “hill” is backward (negative) acceleration. + accel.

– accel.

DISTANCE VERSUS TIME GRAPHS:SOME RULES FOR INTERPRETING........

Is it possible to have zero speed & velocity, but still have acceleration? YES!

Ball thrown in the air

Velocity changesdirection

Velocity is zerofor the instantat the peak

Acceleration is alwaysnonzero and downward

- Velocity is both the speed and direction of an object or body

- Any change in velocity is called an acceleration

- An object with circular motion is accelerating toward the center of the circle

WHAT YOU ARE EXPECTED TO KNOW:

- Review velocity and acceleration and their interpretation from graphs✓

- Distinguish mass from weight and define force

- Investigate the the Law of Inertia

TODAY’S OUTCOMES:FORCE, MOTION AND ENERGY