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crodriguez87
07.03.2020 •
Physics
Sam, whose mass is 72 kg , takes off across level snow on his jet-powered skis. The skis have a thrust of 190 N and a coefficient of kinetic friction on snow of 0.1. Unfortunately, the skis run out of fuel after only 9.0 s. How far has Sam traveled when he finally coasts to a stop?
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Ответ:
Given Information:
Mass = 72 kg
Force exerted by ski = 190 N
coefficient of kinetic friction = 0.1
ski runs out of fuel after = 9 sec
Required Information:
Distance traveled when he stops = ?
d = 179.33 m
Explanation:
The problem can be divided into two parts
Part 1: before running out of fuel
In the first part, the forces acting on Sam are
Ski thrust and Force of friction
Force of friction = kmg
where k is the coefficient of kinetic friction, m is Sam's mass and g is gravity 9.8 m/s²
Force of friction = 0.1*72*9.8
Force of friction = 70.56 N
so the net force acting on Sam is
Fnet = ski thrust - force of friction
Fnet = 190 - 70.56
Fnet = 119.44 N
According to Newton's second law of motion
F = ma
a = F/m
a = 119.44/72
a = 1.65 m/s²
The distance traveled can be found using kinematic equation
d = vi + 0.5at²
d = 0 + 0.5*1.65*9²
d = 66.82 m
The speed at this point is
vf = (d + 0.5at²)/t
vf = (66.82 + 0.5(1.65)(9)²)/9
vf = 14.85 m/s
Part 2: after running out of fuel
When the fuel runs out the ski is no longer applying any force so the only force acting on Sam is force of friction
kmg = ma
kg = a
a = 0.1*-9.8
a = -0.98 (minus sign due to deceleration)
The distance traveled can be found using kinematic equation
2ad = vf² - vi²
d = (vf² - vi²)/2a
d = (vf² - vi²)/2a
d = (0² - 14.85²)/2*-0.98
d = 112.51 m
How far has Sam traveled when he finally coasts to a stop?
We have to sum the distance before and after Sam runs out of fuel because he stops after covering the sum of these distance
d = 66.82 + 112.51
d = 179.33 m
Ответ:
CaCl2
Explanation: