Question

After descending a slope a skier coasts on a level snow for 20 m before coming to rest. If the coefficient of friction between the skies and snow is 0.05, the skier speed at the foot of the slope was
a) 3.1 m/s
b) 4.4 m/s
c) 6.3 m/s
d) 19.6 m/s

Answer 1

so acceleration due to frictional force, a = -μg
(μ=coefficient of friction ; g=gravitational acceleration )
a = -μg = -0.05*9.8

equation of motion $u^{2}$ =  $v^{2}$  + 2as
where
v = final velocity = 0
u = initial velocity
s=displacement = 20m

So,
$u^{2}$ =  $v^{2}$  + 2as
$u^{2}$ =  $v^{2}$  + 2(-μg)20
 -$u^{2}$  =   2(-0.05*9.8)20
 $u^{2}$  =   19.6
u= \sqrt{19.6}
u=4.4

so answer is 4.4m/s