Problem does not make sense km/h at m/s?

  • Thread starter physicshelpme
  • Start date
In summary: Otherwise, it's a confusing and poorly worded problem.In summary, the conversation discusses a problem involving a van traveling at varying speeds and undergoing uniform deceleration. The question involves finding the deceleration, distance traveled, and displacement at different points in time. The conversation also mentions confusion about the units used (km/h and m/s) and the potential for incorrect conversions leading to different answers.
  • #1
physicshelpme
20
0
problem does not make sense km/h at m/s??

1. A van is traveling at 80 km/h at 25 m/s undergoes uniform deceleration when the brakes are applied, slowing to 50 km/h at 10 m/s after 2.1 s. (a) what is the deceleration? (b) How far does it travel during this period? (c) How much farther does it travel before stopping if deceleration remains constant?

Variables= i don't understand what is meant by 80km/h at 25m/s and 50km/h at 10m/s
vi=25m/s? vf=10m/s? t=2.1s 1)find=-a? 2)displacement=? 3)at vf=0 displacement?



Homework Equations


1)i used d=(vi+v2)/2 x t
2)vf=vi+at to find acceleration
3)know how to compute but didnt because I am unsure of my answer what to do with 80km/h what does this mean? please help

The Attempt at a Solution


d=37m
a=-7.14m/s^2
 
Physics news on Phys.org
  • #2
Welcome to PF :smile:
Is that really the question?Name of the textbook?
 
  • #3
yes

yes that's the questions its a homework problem from a document i don't understand what he means by km/h at m/s ?
 
  • #4
IMO, it looks like a rather clumsy attempt at converting 80 km/h to the equivalent velocity of 25 m/s, etc..
 
  • #5
yes, that's what i initially thought, i was thinking that at an initial velocity of 85km/h it changes 25m/s but that does not even make sense because how can velocity change a velocity wouldn't it have to be aceleration
 
  • #6
I think you should use either km/h or m/s in that problem.
 
  • #7
ya that's what i wind up doing thanks man
 
  • #8
It's weird that 80 and 50 kph convert to 22 and 14 m/s, which is off from the m/s values given in the problem. Or, 25 and 10 m/s would convert to 90 and 36 kph. So we would expect two different answers, depending on whether the kph or the m/s values are used -- unless the distances turn out to be the same by sheer coincidence.

As SteamKing said, it's a clumsy attempt at conversion, if that was the the intent.
 

FAQ: Problem does not make sense km/h at m/s?

1. What is the problem with converting km/h to m/s?

The problem with converting km/h to m/s is that the units represent different types of measurements. Km/h measures speed, while m/s measures velocity. Velocity is a vector quantity that includes both speed and direction, whereas speed is a scalar quantity that only measures the magnitude of an object's movement.

2. Why is it important to use the correct units when solving a problem?

Using the correct units is important because it ensures that the answer to a problem is accurate and meaningful. Converting between units that measure different quantities can result in incorrect calculations and lead to misleading results.

3. What is the formula for converting km/h to m/s?

The formula for converting km/h to m/s is: m/s = (km/h * 1000) / 3600. This formula takes into account the different units of measurement for speed and velocity and converts km to m and hours to seconds.

4. Can you provide an example of converting km/h to m/s?

Yes, for example, if you want to convert a speed of 60 km/h to m/s, the calculation would be: m/s = (60 km/h * 1000) / 3600 = 16.67 m/s. This means that 60 km/h is equivalent to 16.67 m/s.

5. Is it possible to convert m/s to km/h?

Yes, it is possible to convert m/s to km/h. The formula for this conversion is: km/h = (m/s * 3600) / 1000. This formula is essentially the reverse of the formula for converting km/h to m/s and takes into account the different units of measurement for speed and velocity.

Back
Top