Speed, Distance, Time Calculations

The aim of this lesson is to be able to use the correct formulas to calculate speed, distance or time

15 mins = 0•25 hour 30 mins = 0•5 hour 45 mins = 0•75 hour Reminder: How to change minutes into a decimal 15 mins = 0•25 hour So: 3 hours 15 mins = 3•25 hours 30 mins = 0•5 hour So: 7 hours 30 mins = 7•5 hours 45 mins = 0•75 hour So: 2 hours 45 mins = 2•75 hours

The 3 formulas for Speed, Time & Distance: Speed x Time Solving for Speed Solving for Time Solving for Distance D S T Remember them from this triangle:

A windsurfer travelled 28 km in 1 hour 45 mins. Calculate his speed.

Answer: His speed was 16 km / hour A windsurfer travelled 28 km in 1 hour 45 mins. Calculate his speed. Distance Time D S T Speed = 28 1•75 = 1 hour 45 mins = 16 km/h Answer: His speed was 16 km / hour

A salesman travelled at an average speed of 50 km/h for 2 hours 30 mins. How far did he travel?

Answer: He travelled 125 km A salesman travelled at an average speed of 50 km/h for 2 hours 30 mins. How far did he travel? D S T Distance = Speed x Time = 50 x 2•5 2 hour 30 mins = 125 km Answer: He travelled 125 km

A train travelled 555 miles at an average speed of 60 mph A train travelled 555 miles at an average speed of 60 mph. How long did the journey take?

Answer: It took 9 hours 15 minutes A train travelled 555 miles at an average speed of 60 mph. How long did the journey take? D S T Distance Speed Time = 555 60 = = 9•25 hours = 9 hours 15 mins Answer: It took 9 hours 15 minutes

Speed Formula # 2 a = v 2 – v1 t Acceleration = (speed 2 – speed 1) ÷ time

Example: Q: What is the rate of acceleration for a car that accelerates from 0 m/sec to 30 m/sec in 10 seconds? a = v 2 – v1 t

Solution: a = ( 30 – 0) = 3m/s 2 10

Try speed formula # 2 A roller coaster’s velocity at the top of a hill is 10m/s. Two seconds later it reaches the top of the next hill with a velocity of 26 meters/second. What is the acceleration of the coaster?

Solution: a = 26 - 10 a=8 m/s 2 2

FLASH BACK NOV. 12 What does the prefix “kilo” stand for? a.) 10 b.) 100 c.) 1,000 Calculate the distance traveled by a mountain goat traveling 10 mph over 3 ½ hours. a.) .35 miles b.) 35 miles c.) 350 miles 3. Calculate the time it took for a bull frog to cross the pond that is 500 meters wide if he is traveling at a speed of 10 meters per second. a.) 50 seconds b.) 5 seconds c.) 500 seconds

Analysis & Conclusion What combinations of height and marble size caused the greatest acceleration of the marble? What caused the least acceleration of the marble? *Acceleration is any change in speed or direction; that means that when the marble slows down or turns it is accelerating.

Complete the section review questions on: #1 -3, p.9 #1 – 3, p.13 Read Ch. 1 in Text Book Complete the section review questions on: #1 -3, p.9 #1 – 3, p.13

Physics Test 1 Add your multiple choice, scantron score (total of 24 pts. Possible) + Your Extended Response score 4 pts possible

Flash Back Nov. 14 Determine the DISTANCE traveled by a herd of horses galloping at a speed of 40 mph over 5 hours. a.) 200 miles b.) 220 m c.) 240 m 2. What does velocity have that speed does not? a.) acceleration b.) direction c.) speed 3.What type of wave moves in the traditional up & down fashion? a.) transverse b.) longitudinal c.) electromagnetic