Can somebody check my work see if I did the steps right?

AI Thread Summary
The discussion focuses on calculating the work done by forces acting on a sled being pulled across a horizontal surface. The user correctly identifies the forces involved and derives the force exerted on the sled to be 63.3N, resulting in a work done by this force of 791J. However, the work done by friction is calculated as -668J, leading to a total work done on the sled of 123J, which is clarified as not being zero despite the sled moving at constant speed. The final consensus confirms that while the initial calculations were on the right track, the total work must account for both the pulling force and friction. The total work done on the sled is ultimately determined to be 123J.
Jac8897
Messages
25
Reaction score
0
A boy pulls a 14.6kg sled 12.5m at a constant speed across a horizontal floor. if the rope makes a 32.4degrees?
angle with the horizontal and the coefficient of friction is .489, what is the work done by each of the forces acting on the sled?
2 days ago - 2 days left to answer.
Additional Details
my work,
from the free body diagram I get

EFy= n+Fsin@-mg=0 "@ = theta"
EFx= Fcos@-f=0 "constant speed"

solve Fy= n=mg-Fsin@
plug it into Fx

friction=un
Fcos@-u(mg-Fsin@)=0
Fcos@-umg+uFsin@=0 >>
Fcos@+uFsin@=umg >>
F(cos@+usin@)=umg>>
F=(umg)/(cos@+usin@)
F=63.3N >>

work of the force
WF=63.3N(12.5)cos0>> WF= 791J

no solve by friction
Fcos@-f=0 >>> f=Fcos@
f=(63.3N)cos(32.5) >> f=53.4N

work of friction
Wf=(53.4N)(12.5M)cos180 >> Wf= -668J

I ignore the N force and the gravity and Fsin@ because they are perpendicular.

is my physics process good?
is my answer right?
thanks
 
Physics news on Phys.org
All the forces you calculated are OK. The total work done on the sled isn't 0. This isn't possible since the sled gains no kinetic or potential energy. Are you sure that both of the forces involved are pulling in the same direction as the motion of the sled?
 
so the total work is W=WF+Wf

W=791J-668J
W=123J
the total work done on the sled is 123J
 
I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
Thread 'A cylinder connected to a hanging mass'
Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
Back
Top