Need help with calculating Gravitational Constant

[JohnDoeJD]

Homework Statement

I would like some help with this question:

A bomb is dropped on a foreign planet. The bomb is dropped from a height of 200m. The bomb traveled the last 100m of the fall in 2.5 seconds. What is the acceleration from the gravitational constant on this planet?


2. The attempt at a solution

I tried making two separate equations, one for the total fall (200m) and one for the 100m fall and combining them but I couldn't get anything because I had too many variables.

 

[cupid.callin]

What is the acceleration from the gravitational constant on this planet?

do you mean "and" ?

 

[JohnDoeJD]

Yes, that's what I meant sorry.

 

[cupid.callin]

write s = ut + .5 at^2 for (t - 2.5) and t seconds
t it the total time of fall

substract 2 eqn's and substitute s_t - s_{t - 2.5} = --- ?

 

[cupid.callin]

Yes, that's what I meant sorry.

gravitational constant remains same everywhere

thats why it is called "UNIVERSAL" gravitational constant !

EDIT:

confirm it yourself by finding its value in this question

 

[JohnDoeJD]

write s = ut + .5 at^2 for (t - 2.5) and t seconds
t it the total time of fall

substract 2 eqn's and substitute s_t - s_{t - 2.5} = --- ?

I did that originally but I couldn't figure out how to isolate A. This is what I had:

100 = 0(t) + 0.5at^2 - 0(t-2.5) + 0.5a(t-2.5)^2

 

[cupid.callin]

rearrange this eqn to a simpler form

use another eqn: 200 = .5at^2

use this eqn to subs. t in first eqn
yu'll get something in √a and a

consider √a as y and and a as y^2 and solve this just like a quadratic eqn!

 

[JohnDoeJD]

Thank you.