Physics : chapter 4

When you look at the speedometer in a moving car, you can see the car's

instantaneous speed

One possible unit of speed is

kilometers per hour or miles per hour

What does the slope of the line at each point represent?

speed

Acceleration is defined as

the rate at which velocity itself changes

Suppose an object is in free fall. Each second the object falls

a larger distance than in the second before.

A pencil lies on your desk. If the Earth is moving around the sun at a speed of 30 km/s, how fast is the pencil moving relative to the desk? How fast is the pencil moving relative to the sun?

0 km/s relative to the desk; 30 km/s relative to the sun

A ball is thrown straight up. At the top of its path its instantaneous speed is

0 m/s

Suppose you are in a car that is going around a curve. The speedometer reads a constant 30 miles per hour. Which of the following is NOT true?

Your velocity is constant.

Speed is

a. always measured in terms of a unit of distance divided by a unit of time. b. a measure of how fast something is moving.

If a freely falling object were somehow equipped with a speedometer, its speed reading would increase each second by

about 10 m/s

In the absence of air resistance, objects fall at constant (unchanging)

acceleration

Acceleration is defined as the CHANGE in

velocity divided by the time interval.