At 6:52 pm PDT Wednesday, July 10, 1996, a large block of granite with an estima

Question

At 6:52 pm PDT Wednesday, July 10, 1996, a large block of granite with an estimated volume of 78,000 cubic yards detached from the cliff between Washburn Point and Glacier Point in Yosemite Valley. The estimated mass of the granite is 80,000 metric tons. Rock falls are a natural and continuous process on the granite cliffs in Yosemite Valley, however, most of the falls result in rock slides. This fall was unique in that it resulted in a projectile type of ballistic free-fall.

Use the information about the rock shelf (sketched above) to determine the value of the launch angle (relative to the horizontal axis) at the point where the rock mass went into projectile motion, as well as the horizontal and vertical displacement of the rock.

In this case, the initial velocity and final velocity are not given. The question asks for launch angle, flight time, vertical and horizontal displacements.

Profile of Yosemite Rock Fall 2000 Detachment Region 1900T 1800 laanch 91700 1600T 1500 1400 1300 -200 100 0 100 200 300 400 Horizontal Distance (m)

Explanation / Answer

From figure, we can see that the rock slides from (-100,1850) to (0,1750)

The projectile will be launched with this angle (being the tangent at launch location) given by

tan(d) = (1750-1850)/(0+100) = -1

d = -45°

Observing the figure, we can see that the projectile motion starts from (0,1750) to (350,1300)

Therefore horizontal displacement, x = 350 - 0 = 350m

and vertical displacement, y = (1300 - 1750) = -450m (-ve indicates downwards)

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.