l Help Homework 4 Begin Date: 9/24/2018 12:01:00 AM-Due Date: 1 (10%) Problem 9:

Question

l Help Homework 4 Begin Date: 9/24/2018 12:01:00 AM-Due Date: 1 (10%) Problem 9: A student standing on a cliff that is a vertical height d 25 ft above the level ground throws a stone with velocity vo 74 ft/ls at an angle o -25 below horizontal. The stone moves without air resistance; use a Cartesian coordinate system with the origin at the stone's initial position. 0/1/2018 i i3900) PM End Date: i 2/17/2018 11:59:00 PM Otheexpertta. 50% Part (a) with what speed, vr in feet per second does the stone strike the ground? Deductions Potential 1 sino cos() tan() ( 789 cotan0asin0 acoso atan0 acotan0 sinh0 coshO tanhO cotanho Attempts remainin (5% per attempt) 0. ODegreesRadians Hints: 16 deduction per hint. Hints remaining

Explanation / Answer

g = 32.17 ft/s^2

conservation of energy(in the absence of air frictional loss of energy):

potential energy(mgh) + kinetic energy(½mv²) = constant

if 'u' is the initial speed of projection: (& 'v' the ground impact speed)

=======> mgh + ½mu² = mg(0) + ½mv²
=======> ½mv² = mgh + ½mu²
=======> v² = 2gh + u² => v = [2gh + u²] = [2(32.17)*25 + 74²] = 84.2 ft/s

therefore v is > u

since the expression for final velocity 'v is independent of the angle °, this implies that can be any value above or below the horizontal. the Ans for 'v' would be the same.


hope this helps

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