You're reading an article about forest fires in california and it features a photograph of firefighters battling a fire on a hil
lside next to a freeway. the firefighters are at the bottom of the hill using a firehose to control a fire that's in the middle of the hill. you're curious how fast the water is exiting the nozzle. analyzing the photograph in photoshop, you determine that the firehose nozzle is being held 2.1 m above the ground and is angled 43 ∘ above the horizontal. furthermore, the water from the hose lands on the hill 30 m from the feet of the firefighters. the article mentions that the grade of the hill is 37%, which corresponds to a slope of 20∘ above the horizontal. what is the speed the water when it exits the hose?
1 answer:
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m = mass of the box
N = normal force on the box
f = kinetic frictional force on the box
a = acceleration of the box
μ = coefficient of kinetic friction
perpendicular to incline , force equation is given as
N = mg Cos30 eq-1
kinetic frictional force is given as
f = μ N
using eq-1
f = μ mg Cos30
parallel to incline , force equation is given as
mg Sin30 - f = ma
mg Sin30 - μ mg Cos30 = ma
"m" cancel out
a = g Sin30 - μ g Cos30
inserting the values
1.20 = (9.8) Sin30 - (9.8) Cos30 μ
μ = 0.44
