Displacement and average velocity

In summary, the hiker traveled south for a total of 4 hours, with an average velocity of .75 km/h for 1.5 hours and an average velocity of .90 km/h for 2.5 hours. The total displacement for the trip is 3.375 km to the south. The units for velocity and time were consistent, so no conversion was necessary.
  • #1
JMWM
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0

Homework Statement


A hiker travels south a long a straight path for 1.5 h with an average velocity of .75 km/h. then travels south for 2.5 h with an average velocity of .90 km/h. What is the hiker's displacement for the total trip?


Homework Equations





The Attempt at a Solution


For the answer I have 3.4 km to the south.
but hm, I think I copied the question wrong. I have a feeling that I was supposed to have another coordinate sign besides south... so I'm not sure.
 
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  • #2
Well, your answer is correct (3.375 km i get before rounding) if the question is as you've written it!
 
  • #3
oh ok. cool.
but oh gosh, let me try it. but well I'm not really sure what to do.
 
  • #4
Ahh, so you mean that's the answer the book gives? Ok, well what equation do you know relating velocity, distance and time?
 
  • #5
well its a review sheet, the teacher gave it to me.

distance/t
or do I use: av. velocity= total distance/time
 
  • #6
Yes, use av.velocity=distance/time, but remember to calculate the two parts separately, and then add them up at the end to arrive at a total distance.
 
  • #7
awesome.
another question, for instance 1.5 h, ok do I convert that into minutes? and if so do I take the .5 as half or as 50, as in fifty minutes. 1 hour and fifty minutes or 1 and a half or 90 minutes or 110 minutes?
wow, I ask a lot of questions.
 
  • #8
Well, you would take 1.5h as one and a half hours, or 1 hr 30 mins. However, in this instance, you don't need to convert.

The units of velocity are given as km/hr, and the times in hr, so, if we look at the equation: s=vt, and consider putting the units in, we get s (km) = v(km/hr)*t(hr). Notice that the hr's will cancel, and give a result in km, which is what is required.

For calculations like this, as long as you keep to the same units throughout, the answer will be correct. (A problem would occur if, for example, the velocity was in km/hr and the time measured in seconds. In this case we would have to convert units)

Hope this is clear!
 
  • #9
yeah that's what I noticed.
but well ok for km/h I get 1.65 and then for hours 4.
so this is my equation: 1.65 km/h /4h and then I get .4125...
eek. I know I'm doing something wrong.
 
  • #10
Re-read post #6. You need to do one calculation to work out the distance for the first part: traveling along a straight path for 1.5 h with an average velocity of .75 km/h, and another calculation for the second part: traveling for 2.5 h with an average velocity of .90 km/h.

When you have these two distances, add them up and you will get the required answer.
 
  • #11
ooops, sorry. got you. thanks!
 

1. What is displacement?

Displacement is the distance and direction of an object's change in position, measured from its initial position to its final position. It is a vector quantity, meaning it has both magnitude and direction.

2. How is displacement different from distance?

Distance is a measure of how far an object has traveled, while displacement takes into account the direction of movement. Distance is a scalar quantity, meaning it only has magnitude.

3. What is average velocity?

Average velocity is the change in displacement over a specific time interval. It is a vector quantity, calculated by dividing the change in displacement by the change in time.

4. How is average velocity different from instantaneous velocity?

Average velocity is the overall rate of change in displacement over a specific time interval, while instantaneous velocity is the velocity at a specific moment in time. Average velocity is calculated using the total displacement and time, while instantaneous velocity is calculated using the slope of the displacement-time graph at a specific point.

5. How does displacement affect average velocity?

Displacement is directly related to average velocity. As displacement increases, average velocity also increases, as long as the time interval remains the same. This means that a greater change in position results in a higher average velocity.

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