What is your average speed from Houston back to San Antonio?

In summary, the conversation discusses solving physics problems involving distance, time, and speed. It includes a calculation for average speed, solving a problem involving a thrown stone, and calculating the time spent in different parts of a basketball player's jump. The conversation also mentions using the quadratic formula to solve a problem and the preference of avoiding it.
  • #1
hytuoc
26
0
Plz show me how to do #1? and please check my work on #2 and 3. thanks so much! :smile:

1) You drive on Interstate 10 from San Antonio to Houston, half the time at 55km/h and the other half at 90km/h. On the way back you travel half the distance at 55km/h and the other half at 90km/h. What is ur averge speed rom Houston back to San Antonio?

Plz check my work below to see whether if I did it right?
2) A hoodlum throws a stone vertically downward w/ an initial speed of 12.0 m/s from the roof of a building, 30.0 m above the ground. (a) How long does it take the stone to reach the ground ?
(b) What is the speed of the stone at impact?

a) x = xi +vi t + 1/2 at^2
0= 30m + 12m/s t -1/2 * 9.8*t^2
t = 3.99 s or 4.0 s
b) vf = vi + at
= 12 - 9.8 (4s) = -27.2 m/s
****did I do (b) correctly?

3) A basketball player, standing near the basket to grab a rebound, jumps 76.0 cm vertically. How much (total) time does the player spend (a) in the top 15.0 cm of this jump and (b) in the bottom 15.0 cm? Does this help explain y such players seem to hang in the air at the tops of their jumps?

a) xf = xi +vi*t+1/2 at^2
76 = 0 + 0 + 1/2 (9.8) t ^2
t = 3.94 s
61 = 0 + 0 + 1/2 (9.8) t^2
t = 3.53 s
=> t= .41s <- time the player spent in the top 15.0 cm
b) 15 = 0 + 0 + 1/2 (9.8) t^2
t = 1.75 s
 
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  • #2
On number 2-a, you may have calculated the time wrong. Make sure you use the quadratic equation.

You should get 4.9t^2 + 12t - 30 = 0. Thats all I'll say :)

Take into acct that I am also a physics student and am not too confident in what I am saying..
 
Last edited:
  • #3
Why use quadradic formula?
That thing is nasty I try to stay away from it, find Vf first then you do not have to use that nasty thing. :smile:
 

What is your average speed from Houston back to San Antonio?

1. How is average speed calculated?

Average speed is calculated by dividing the total distance traveled by the total time it took to travel that distance. It is measured in units of distance per unit of time, such as miles per hour or kilometers per hour.

2. How do you determine the total distance traveled?

The total distance traveled can be determined by using a map or GPS device to measure the distance between Houston and San Antonio. Alternatively, the distance can be calculated by multiplying the average speed by the total time traveled.

3. How do you keep track of the total time traveled?

The total time traveled can be kept track of by using a stopwatch or timer, or by recording the start and end times of the trip. It is important to include all stops and breaks in the total time, not just the time spent driving.

4. Does traffic affect average speed?

Yes, traffic can affect average speed. If there is heavy traffic or road construction along the route, it can slow down the overall speed and increase the total time traveled.

5. Is average speed the same as constant speed?

No, average speed is the total distance traveled divided by the total time, while constant speed is the speed at which an object travels without any changes in its velocity. Average speed can change throughout a trip, while constant speed remains the same.

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