DO NOW: WHAT ARE THE TWO
MEANINGS OF THE WORD “TIME”
IN PHYSICS?
TICK TOCK, TICK TOCK, TICK TOCK
TIME….
• It can mean either a moment in time
like when you as, “What time is it?”
OR….
• It can mean a quantity of time, for
example how long did something
take to occur?
We use the second (sec) as
our basic unit of time.
SPEED & CONSTANT SPEED
• What is the difference?
• Speed describes movement from one place to
another over time; we say it’s the distance divided
by time.
• Constant speed is a maintained speed that does
not change. This means the same distance is
traveled every second.
Why do we use v?
V stands for velocity, which
indicates that you know
direction as well as speed.
WHAT ARE THE UNITS?
• Meters per second
• Kilometers per hour
• Centimeters per second
• Miles per hour
• Inches per second
• Feet per minute
NOW LET’S PRACTICE…
1. What is the average speed of a car that traveled
300.0 miles in 5.5 hours?
2. A bicyclist, traveling at 22 miles per hour, rides a
total of 44 miles. How much time, in hours, did it
take?
3. How far can a person run in 15 minutes if he or she
runs at an average speed of 16km/hr? Hint make
sure your time is in the same units!
4. You ride your bike for a distance of 30 km. You
travel at a speed of 0.75 km/minute. How many
minutes does this take?
• Answers:
1. speed = distance / time….
300 miles/5.5 hours =
2. Time = distance /speed
44 miles/22 miles/hour
3. Distance = speed * time
15 minutes * 1 hour/60 minutes = 0.25 hours
16 km/hour * 0.25 hours =
4. Time = distance /speed
30 km / 0.75 km/minute
HOMEWORK
• Page 21 numbers 3, 4, and 5