Solving a Robot Probe Homework Problem on Mars

[inedhelpinphy]

Homework Statement

a robot probe drops a camara off the rim of a 239 m high cliff on mars, where the freefall acceleration is -3.7 m/s^2. a. fiind the velocity wl which the camara hits the ground. b. find the tiime required for it to hit the ground.

Homework Equations

vf^2= vi^2+2ad

The Attempt at a Solution

a=-3.7m/s^2
d=239m
vi=0m/s
vf=? ned to find
t=?

vf^2=vi^2+2ad
vf^2=-1786.6

 

[thaer_dude]

d is actually -239m since it's falling. which means starting from 239 m and falling down to 0m so the change is -239m. the vf you will then calculate is actually negative like the acceleration since, again, it is falling downwards on the y axis

 

[tramar]

Looks good except your displacement should be negative, $$\Delta d=0-239m$$

That will make your value for $$v_f^2$$ positive and you should be able to proceed.

 

[inedhelpinphy]

tyvm! but i want to just ask 1 more question... so then will the final velocity be negative?b/c it is falling

 

[thaer_dude]

yes the vf will be negative, like i said in my previous reply >_>