Respuesta :
Answer
given,
mass of sled = 10 Kg
Force applied by girl = ?
angle of inclination = 30°
distance = 15 m
Sled is moving with constant speed hence acceleration will be equal to zero.
now,
F - mg sin θ - f = m a
F - mg sin θ - f = 0
F - mg sin θ = f
where f is the frictional force acting opposite to the applied force
mg sin θ is the component of the weight which is opposing the motion of the sled
now,
f = F - mg sin θ
f = 75 - 10 x 9.8 x sin 30°
f = 26 N
now,
Work done = f. s cos ∅
where ∅ is the angle between frictional force and displacement which is equal to 180°
W= 26 x 15 x cos 180°
W = -390 J
work done by frictional force is equal to W = -390 J
The work done by child to move the system is 974.25 Joules.
The work done is given by an expression shown below,
[tex]Workdone=Force*Distance*Cos\theta[/tex]
Where [tex]\theta[/tex] angle between force and direction of displacement.
Given that, [tex]Force=75N,Distance=15m,\theta=30[/tex]
Substitute in above expression.
[tex]Workdone=75*15*cos(30)\\ \\ Workdone=75*15*0.866\\ \\ Workdone=974.25Joule[/tex]
Hence, the work done by child to move the system is [tex]974.25[/tex] Joules.
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