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Physical Science II - Mph of a dragster at the finish line of a race- ?

student_2018

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Joined
Feb 8, 2018
Messages
2
Please assist me with the following question :


One "G" of acceleration is the rate at which an object will accelerate if it is dropped near the Earth's surface, ignoring air resistance. One "G" of force is the force necessary to generate one G of acceleration (although "G" is not an official SI unit of force).

Suppose you built a rocket-powered dragster which could produce a constant acceleration, for a few seconds, that was similar to the acceleration that Cmdr Shepard experienced for the first several minutes of his flight.
On one pass, your dragster produces a constant acceleration of exactly 5.97 G's throughout the whole race.
How fast would your dragster be going at the end of a drag strip that was exactly 1000 feet long?
Your answer must be in miles/hour.

The work I did so far is:
√2(58.506 m/s²)(1000m) = 342.07016824 m/s² converted to MPH = 765.1892 rounded to 765 MPH


Capture.jpg
 

Subhotosh Khan

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Jun 18, 2007
Messages
18,089
Please assist me with the following question :


One "G" of acceleration is the rate at which an object will accelerate if it is dropped near the Earth's surface, ignoring air resistance. One "G" of force is the force necessary to generate one G of acceleration (although "G" is not an official SI unit of force).

Suppose you built a rocket-powered dragster which could produce a constant acceleration, for a few seconds, that was similar to the acceleration that Cmdr Shepard experienced for the first several minutes of his flight.
On one pass, your dragster produces a constant acceleration of exactly 5.97 G's throughout the whole race.
How fast would your dragster be going at the end of a drag strip that was exactly 1000 feet long?
Your answer must be in miles/hour.

The work I did so far is:
√2(58.506 m/s²)(1000m) = 342.07016824 m/s² converted to MPH = 765.1892 rounded to 765 MPH


View attachment 9118
Why did you assume a = 6*g (instead of 5.97*g)? And:

Dx = 1000 ft = 304.8 meters
 

student_2018

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Feb 8, 2018
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2
The picture was an example from the book on how to solve the problem. I can't figure it out :(
 

Subhotosh Khan

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The picture was an example from the book on how to solve the problem. I can't figure it out :(
Did you adjust for the length to be converted to meters?
 

Whutever42

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Jan 19, 2018
Messages
14
Instead of making G into metric units and having to convert the 1000ft into meters use 32ft/sec[SUP]2 [/SUP]and you would only have to convert ft/sec into miles/hour
 

chris84567

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Joined
Jan 23, 2018
Messages
12
v[SUB]f[/SUB][SUP]2[/SUP]=v[SUB]i[/SUB][SUP]2[/SUP]+2ad
v[SUB]i [/SUB]is 0
v[SUB]f[/SUB] is what you are looking for
a is g*5.97 or 5.97*32=191 feet per second[SUP]2[/SUP] (stop being a commy and use some english units)
d is 1000 feet

v[SUB]f[/SUB]=sqrt(2*191*1000) feet/second
v[SUB]f[/SUB]=618 feet/second

Convert to mph

618 feet/second * 1 mile/5280feet * 3600 hour/ 1 second = 421 mph
 
Last edited:

j-astron

Junior Member
Joined
Jan 10, 2018
Messages
181
v[SUB]f[/SUB][SUP]2[/SUP]=v[SUB]i[/SUB][SUP]2[/SUP]+2ad
v[SUB]i [/SUB]is 0
v[SUB]f[/SUB] is what you are looking for
a is g*5.97 or 5.97*32=191 feet per second[SUP]2[/SUP] (stop being a commy and use some english units)
d is 1000 feet

v[SUB]f[/SUB]=sqrt(2*191*1000) feet/second
v[SUB]f[/SUB]=618 feet/second

Convert to mph

618 feet/second * 1 mile/5280feet * 3600 hour/ 1 second = 421 mph
1) It's commie :p

2) You guys are the worst for still using Imperial units, and the OP's teacher is a sadist for assigning a problem with mixed units

3) You can guide posters towards a solution, but don't do people's homework for them on this site; they don't learn any physics or math if you just provide them with the solution.
 

chris84567

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Joined
Jan 23, 2018
Messages
12
2) You guys are the worst for still using Imperial units, and the OP's teacher is a sadist for assigning a problem with mixed units
there are no mixed units

if you cant use both systems of measurement you obviously don't understand the problem
 

j-astron

Junior Member
Joined
Jan 10, 2018
Messages
181
there are no mixed units

if you cant use both systems of measurement you obviously don't understand the problem
Uh, ok. Check your assumptions at the door. I understand the problem fine, and can use both systems of measurement fine. The Imperial one is just mostly stupid and outdated, because there are arcane conversion factors between different units of the same dimension (e.g feet to miles), rather than multiples of 10. And the rest of the world has adopted an international standard.

The fact that OP only seemed to know the value of g in SI units and substituted that in, despite the fact that the other units in the problem were given in Imperial, suggested to me that maybe his/her teacher was mixing and matching unit systems. Pick one system and stick to it. Either way, I was being mostly facetious with my points 1 and 2. My point 3 was the one that was actually important, i.e. in the future please do not provide complete solutions to problems on this site.
 
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