# Static equilibrium Cliff Climber

#### electricblue

1. Homework Statement

Mountaineers often use a rope to lower themselves down the face of a cliff (this is called rappelling). They do this with their body nearly horizontal and their feet pushing against the cliff (the figure (Intro 1 figure) ). Suppose that an 84.7-{\rm kg} climber, who is 1.75 {\rm m} tall and has a center of gravity 1.1 {\rm m} from his feet, rappels down a vertical cliff with his body raised 40.7^\circ above the horizontal. He holds the rope 1.54 {\rm m} from his feet, and it makes a 25.5^\circ angle with the cliff face.

Part A
What tension does his rope need to support?

Part B
Find the horizontal component of the force that the cliff face exerts on the climber's feet.
"[URL [Broken]

Part C
Find the vertical component of the force that the cliff face exerts on the climber's feet.

Part D
What minimum coefficient of static friction is needed to prevent the climber's feet from slipping on the cliff face if he has one foot at a time against the cliff?

2. Homework Equations
$$\sum$$$$\tau$$=0
$$\sum$$Fx=0
$$\sum$$Fy=0

3. The Attempt at a Solution

For Part A i did 3 times and got the wrong solution... but i still cannot figure out why.

$$\sum$$$$\tau$$= 1.1 x mg x cos40.7 - T cos 71.8 x 1.54
answer i got was T = 1439.15

Part B i used n = Fx = 472 x cos 67.5 = 180.62

Last edited by a moderator:
Related Introductory Physics Homework Help News on Phys.org

"Static equilibrium Cliff Climber"

### Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving