Measurement II

Measurement II

Identifying and Describing Change

Observe, collect evidence, and measure to identify change

To measure and describe change, scientists use numbers and ratios ( a
comparison of numbers)

Fractions and percentages are examples of ratios.

Example: In a group of 8 trees, 2 died. This can be expressed as 2:8, 2/8, ¼, or
25%

Density

Ratio that compares the amount of mass in an object to the volume of the object

The most well known density of a substance is that of water which is 1 g/mL.

Anything with a higher density will sink in water, and anything with a density that
is less than 1 will float.

Speed

Ratio that compares the distance an object travels to the time it takes to travel
that distance.

In other words, Speed = Distance / Time

A special kind of ratio called a rate. Rates usually involve a change in some
quantity over time.

Velocity

Velocity is similar to speed except that velocity is a type of vector so it must
include both the speed and direction of the object. This is an important
description to use in various situations.

For example, a tornado has been spotted in the area near Roulette travelling east
at 30 mph. Imagine if that description only included the speed of 30 mph and
did not include the direction.

Velocity is calculated using the same formula as speed, but it must include the
direction.

Acceleration

A measurement of the change in velocity. This can mean many things. In order
to change velocity, an object can speed up, slow down, or change direction. If
the acceleration is positive, it is speeding up. If the acceleration is negative, it is
slowing down. If there is no change in speed, but there is a change in direction,
the object is accelerating (a car going around a curve).

Acceleration = (Final Speed - Initial Speed) / Time