Got Homework?
Connect with other students for help. It's a free community.
Here's the question you clicked on:
 0 viewing
Robinronaldo
Group Title
A rock dropped from a cliff covers onethird of its total distance to the ground in the last second of its fall. Air resistance is negligible. How high is the cliff?
 one year ago
 one year ago
Robinronaldo Group Title
A rock dropped from a cliff covers onethird of its total distance to the ground in the last second of its fall. Air resistance is negligible. How high is the cliff?
 one year ago
 one year ago

This Question is Open

exploringphysics Group TitleBest ResponseYou've already chosen the best response.0
distance covered inlast sec. is v+1/2g=v+5=1/3h; v=([2h/g]^1/2 1)g; v^2=(h/5+12[h/5]^1/2)g^2; solve these and eliminatte v you get h
 one year ago

Robinronaldo Group TitleBest ResponseYou've already chosen the best response.0
@ashwinjohn3 what would be the answer in your opinion?
 one year ago

shamim Group TitleBest ResponseYou've already chosen the best response.1
ur answer will b 148.48 m
 one year ago

shamim Group TitleBest ResponseYou've already chosen the best response.1
can i explain my work
 one year ago

ashwinjohn3 Group TitleBest ResponseYou've already chosen the best response.0
ok use the equation....... Diplacement @ nth second=u+ a(2n1)/2
 one year ago

shamim Group TitleBest ResponseYou've already chosen the best response.1
i wanna use the equation\[h=ut+ \frac{ 1 }{ 2 } g t ^{2}\]
 one year ago

shamim Group TitleBest ResponseYou've already chosen the best response.1
for full height u=0
 one year ago

shamim Group TitleBest ResponseYou've already chosen the best response.1
and my equation become \[h=0+\frac{ 1 }{ 2 } g t ^{2}\]
 one year ago

shamim Group TitleBest ResponseYou've already chosen the best response.1
\[h=\frac{ 1 }{ 2 } \times 10 \times t ^{2}=5 \times t ^{2}\]
 one year ago

shamim Group TitleBest ResponseYou've already chosen the best response.1
its my 1st equation
 one year ago

shamim Group TitleBest ResponseYou've already chosen the best response.1
now i wanna write another equation for 1st 2/3 h height
 one year ago

shamim Group TitleBest ResponseYou've already chosen the best response.1
\[\frac{ 2 }{ 3 }h=ut+\frac{ 1 }{ 2 } \times g t ^{2}=\frac{ 1 }{ 2 } \times 10 \times (t1)^{2}\]
 one year ago

shamim Group TitleBest ResponseYou've already chosen the best response.1
now u hv to solve these 2 equation to get time t and then u will get the height h
 one year ago

agent0smith Group TitleBest ResponseYou've already chosen the best response.0
You will get two values for t, but one of them will be less than 1 second, making it invalid, as you can see from the question "covers onethird of its total distance to the ground in the *****last second***** of its fall" Solve the two equations shamim gave you, by substituting the first one into the second, then solve for t. The second equation comes from the fact that, if it covers one third of the total distance in the last second, then it must cover the initial 2/3rds of the total distance in (t1) seconds. \[h = \frac{ 1 }{ 2} g t ^{2}\] \[\frac{ 2 }{ 3} h = \frac{ 1 }{ 2} g (t  1) ^{2}\]
 one year ago

chongkhengwye Group TitleBest ResponseYou've already chosen the best response.0
Say the height of the cliff is H, time take for fall is T, and g is the acceleration of freefall. \[H=\frac{ 1 }{ 2 }gT ^{2}\]  (1) \[\frac{ 2 }{3} H=\frac{ 1 }{ 2 }g(T 1)^{2}\]  (2) Solving you will get 2 answer for T: 0.551 s and 5.45 s But T>1, Hence H = 146 m
 one year ago
See more questions >>>
Your question is ready. Sign up for free to start getting answers.
spraguer
(Moderator)
5
→ View Detailed Profile
is replying to Can someone tell me what button the professor is hitting...
23
 Teamwork 19 Teammate
 Problem Solving 19 Hero
 Engagement 19 Mad Hatter
 You have blocked this person.
 ✔ You're a fan Checking fan status...
Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.