A 54 kg skier coasts up a snow-covered hill that makes an angle of 25° with the horizontal. The initial speed of the skier is 5.2 m/s. After coasting a distance of 1.9 m up the slope, the speed of the skier is 2.5 m/s.
(a) Find the work done by the kinetic frictional force that acts on the skiis.
(b) What is the magnitude of the kinetic frictional force?
2007-03-29 05:53:37 · 1 answers · asked by buttrefly007 1 in Science & Mathematics ➔ Physics
Using conservation of energy
.5*m*v1^2=.5*m*v2^2+m*g*h+FE
where
v1 is starting speed 5.2
v2 is the speed after coasting 1.9 m upslope
h is the vertical gain: sin(25)*1.9 (0.803)
FE is the work done by friction
doing some algebra
FE=54*(.5*(5.2^2-2.5^2)-
9.81*.803)
=136 J
The magnitude of the force is found using the equation
FE=F*d
=136/1.9
=71.6 N
Just for fun, let's compute µ
m*g*cos(25)*µ=F
µ=71.6/(54*9.81*cos(25))
µ=0.149
j
2007-03-29 06:05:15 · answer #1 · answered by odu83 7 · 1⤊ 0⤋