# Homework Help: Average speed

1. Sep 4, 2015

### iamchattha

1. The problem statement, all variables and given/known data
A racing car accelerates uniformly through three gears, changes with the following average speed
20 for 2.0 s
40 for 2.0 s
60 for 6.0 s
what is the overall average speed of the car?
a) 12
b) 13.3
c) 40
d) 48
e) 37
2. Relevant equations

3. The attempt at a solution

2. Sep 4, 2015

3. Sep 4, 2015

### iamchattha

could not think of a possible formula.

4. Sep 4, 2015

### Staff: Mentor

What's the most basic definition of average speed?

5. Sep 4, 2015

### iamchattha

distance traveled by an object during an interval

6. Sep 4, 2015

### William White

err, everybody in the whole world knows that

speed = miles per hour (or km per hour)

so you know one formula!

7. Sep 4, 2015

### iamchattha

but in the case of above mentioned question three speeds and vales of time are give...not distance and time....i have to drive average speed using 3 vales of speed and time

8. Sep 4, 2015

### William White

okay
you are in a car that goes 20 miles per hour for 2 hours; then 40 miles per hour for 2 hours and then 60 miles an hour for 6 hours.

how long has elapsed (in hours) and how far has the car gone (in miles) ?

9. Sep 4, 2015

### iamchattha

could it be done in a way that i first find out 3 values of distance( x= vt) using the above data and then taking 10 s as total time I find average speed?

10. Sep 4, 2015

### William White

Q1) a car travels at 20mph for 2 hours. How far has it gone?

11. Sep 4, 2015

### iamchattha

40 miles

12. Sep 4, 2015

### iamchattha

it would be 480 miles in total

13. Sep 4, 2015

### William White

edit, you know how to do it now.

14. Sep 4, 2015

### iamchattha

are you referring to this
"could it be done in a way that i first find out 3 values of distance( x= vt) using the above data and then taking 10 s as total time I find average speed?"

15. Sep 4, 2015

### William White

I'm referring to the fact you now know the total distance and the total time so you know the speed.

Don't overcomplicate this!

16. Sep 4, 2015

### Staff: Mentor

Exactly!

Just calculate the total distance traveled.