an attendant pushes a 25kg empty wheelchair starting from rest a 22 degree ramp
ID: 1790198 • Letter: A
Question
an attendant pushes a 25kg empty wheelchair starting from rest a 22 degree ramp which is 35 meters long. at the top of the ramp the chair has a speed of 2,0 m/s
a. what was the total work done
b. what was the average net force applied to the wheelchair
2. a 0.123kg ball is thrown vertically downward from a clifftop with a speed of 21.5m/s it hits the ground with a speed of 57.2m/s the average force of air resistance on ht e ball is 0.75N
a. find the height of the cliff
b. if the same ball is thrown vertically upwards from the top edge of the clifftop with the same speed of 21.5m/s calculate the maxium height the ball reaches above the ground assuming the same average force of air resistance
Explanation / Answer
from work energy relation
work done = change in kinetic energy
W = KEf - KEi
final kinetic energy KEf = (1/2)*m*vf^2
vf = final speed = 2 m/s
initial kinetic energy KEi = (1/2)*m*vi^2
vi = inital speed = 0
work = (1/2)*25*(2^2-0) = 50 J
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b)
from definition of work
work = Fnet*displacement
50 = Fnet*35
Fnet = 1/43 N <<<<--------ANSWER
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2)
along vertical
Fnet = f - mg = -ma
acceleration ay = (0.75-(0.123*9.8))/0.123 = -3.7 m/s^2
vy^2 - voy^2 = 2*ay*y
57.2^2-21.5^2 = 2*3.7*h
height h = 380 m
(b)
Fnet = f - mg = -ma
acceleration ay = (0.75-(0.123*9.8))/0.123 = -3.7 m/s^2
final speed at maximum height vy = 0
vy^2 - voy^2 = 2*ay*y
0-21.5^2 = -2*3.7*h
height h = 62.5 m
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