On planet K, there is essentially no atmosphere, so objects in freefal

Question

On planet K, there is essentially no atmosphere, so objects in freefall experience no air friction. At time t = 0, an object released from rest accelerates downward at a uniform rate: its downward speed uniformly increases. At time t = 2 second, the object has fallen a distance D in meters from its original height. At time t = 5 second, the object is 75 meters below its original height, and is moving at a downward speed of v in meters per second.

In the table below, select values of D, the distance below the initial height at t = 2 seconds, and v, the downward speed at t = 5 seconds, that are consistent with the information provided. Make only two selections, one in each column.

In the table below, select values of D, the distance below the initial height at t = 2 seconds, and v, the downward speed at t = 5 seconds, that are consistent with the information provided. Make only two selections, one in each column.

Shrivathsan · Answer

Hi  mikemcgarry ,

t=5 distance is 75
75/5 = 15 meters per second.
But we don't have that in option. is it because  "accelerates downward at a uniform rate" ?

mikemcgarry · Answer

Dear Shrivathsan , I'm happy to respond. :-)

When you divide total distance by total time, that's average velocity over the entire five second interval. You have 100% correctly calculated the average velocity, but unfortunately, that's not the "v" for which the question was asking. You perfectly calculated the answer for a question that was not asked. Does this make sense? Mike :-)

vsvikas · Answer

hi Mike,
I did not get the solution. could u help?

mikemcgarry · Answer

Dear vsvikas , I'm happy to respond. :-)

You can find a full explanation here: GMAT Integrated Reasoning: Two-Part Analysis Practice Questions This question is #5 on that page. Let me know if you have any question about the explanation on that page. Mike :-)

JoeAa · Answer

Please can we have the explanation.

sayan640 · Answer

I used physics to solve this.

After t=2 , D= 1/2 *g *t^2 = 1/2 * g* 4 = 2*g And after t=5 , 75 = 1/2 g * 5^2 hence , g= 6 After t= 5 sec , v= gt = 6t= 6*5 =30 After t= 2 sec , D = 2g = 2*6 = 12 chetan2u GMATinsight KarishmaB , I know I am NOT supposed to bring in external knowledge ; But I was totally clueless and this idea came into my mind. I solved it fairly quickly in under 3 minutes. Formuale used => v= u + gt and s= ut + 1/2 gt^2 ; u can be taken as zero here as the ball is just released with no initial velocity ; v is the final velocity and s is total displacement ( D in this case).

GMATinsight · Answer

with all due respect to the makers of this question, I wouldn't mark this question as a relevant question for GMAT prep. This question is more of physics question than a Quant question.

I haven't witnessed a question in GMAT based on constant acceleration or deceleration. All official ones are the constant speed questions so I have my doubts placed on quality of this question in reference to it's relatability with GMAT context.

GMATinsight · Answer

solution to this question posted on another forum Screenshot 2024-06-16 at 12.17.29 PM.png FOr those who like to fiddle with harder questions for fun...

Oppenheimer1945 · Answer

On planet K, there is essentially no atmosphere, so objects in freefall experience no air friction. we should also consider gravitational potential mikemcgarry GM/R Right?

We can't assume S=ut+1/2 gt^2 will work in the alien planet

kittle · Answer

Poor quality question
 Sajjad1994  - we should remove such irrelevant questions. This is a IITJEE question where equation of Kinematics from Physics are required to solve the question

chetan2u · Answer

Agreed, and the question is being archived.

On planet K, there is essentially no atmosphere, so objects in freefal

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