a sledge loaded with bricks has a total mass of 18.0 kg and is pulled at constant speed by a rope inclinded at 20degrees above horizontal. The sledge moves a distance of 20.m on a horizontal surface. the coefficient of kinetic friction between the sledge and surface is .500.
a). what is the tension in the rope?
b). How much work is done by the rope on the sledge
c) what is the mechanical energy lost due to friction
Thankyou!!!
2007-10-04 10:35:19 · 1 answers · asked by Ashley P 1 in Science & Mathematics ➔ Physics
Look at a FBD of the sledge in both the horizontal and vertical since the speed is constant and the thing stays on the ground there is no acceleration, therefor F=m*a=0, or the sum of the forces is zero
in the horizontal
Tension*cos(20)-friction=0
friction is the normal force times mu.
In the vertical,
Normal force is
Normal = m*g-Tension*sin(20)
(18*9.81-T*sin(20))*.5=
T*cos(20)
T=18*9.81/(2*cos(20)+sin(20))
79.5 N
The work done is equivalent to loss due to friction
79.5*cos(20)*20
j
2007-10-04 10:43:31 · answer #1 · answered by odu83 7 · 0⤊ 0⤋