Answer:
a. 14.68m/s
b. 1.043N
Explanation:
a.
Given
Mass = m = 144g = 0.144kg
Height = h = 11m
Using energy conservation,
½mv² = mgh where g = 9.8m/s² ----- divide both sides by m
½v² = gh ---- divide both sides by ½
v² = 2gh
v = √2gh
v = √(2 * 9.8 * 11)
v = 14.68332387438212m/s
v = 14.68m/s ----- Approximated
b.
v = 7.5m/s
By definition, “the average force of air resistance,”
When work done against air resistance is solved by multiplying height by the average force of resistance ------ by definition
i.e. W = -Fh
Minus is used because F and h points to different direction (when viewed as vectors).
This is proved by:
W = Fhcos(180) because h points toward the direction of motion (downward) while F points opposite.
W = Fh * -1
W = Fh
Using energy conservation,
mgh - Fh = ½mv² ---- Make Fh, the subject of formula
Fh = mgh - ½mv² ---- Divide through by h
F = mg - mv²/2h
F = 0.144 * 9.8 - 0.144 * 7.5²/(2 * 11)
F = 1.043N
