T I C K T O C K , T I C K T O C K , T I C K T O C K

DO NOW: WHAT ARE THE TWO MEANINGS OF THE WORD “TIME” IN

PHYSICS?

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 /speed30 km / 0.75 km/minute

HOMEWORK

• Page 21 numbers 3, 4, and 5