Homework Help: math

Posted by amy on Monday, July 25, 2011 at 7:05pm.

a spaceship leaves the alien mother-ship and begins descending to earth. it descends 64m during the first second and 7m less during each second afterward. if the aliens invade after 10s, how far did the ship descend?

math - Damon, Monday, July 25, 2011 at 7:54pm
Vi = -64 m/s (velocity is down)
dv/dt = a = +7m/s^2 (acceleration is up)

h = hi + Vi t + (1/2) a t^2
h - hi = -64(10) + 3.5 (100)
= -640 + 350
= - 290
so it went down 290 meters
math - kristen, Monday, July 25, 2011 at 8:44pm
would there be any formulas you would have to use to get this answer for grade 11 math
math - Damon, Monday, July 25, 2011 at 10:30pm
h = hi + Vi t + (1/2) a t^2
usually
x = Xi + Vi t + (1/2) a t^2
math - Anonymous, Friday, July 29, 2011 at 11:51am
In first one second it descends 64 m ,
Next one second it descends =(64-7)=57 m
Then next one second it descends = ( 57-7)=50 m,
4th second it descends =50-7=43 m
5th second it descends = 43-7=36 m.
6th second it descends = 36-7=29 m.
7th second it descends = 29- 7= 22 m
8th second it descends = 22-7=15 m
9th second it descends = 15-7=8 m.
10th second it descends = 8-7=1 m

Total distance covered by it= 64+57+50+43+36+29+22+15+8+1= 325 m

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