Please check if I did it right?

[yaho8888]

Homework Statement

A skier starts from rest at the top of a 26 degree slope 1.3Km long.
how long does it take to reach the bottom? (no friction)





The attempt at a solution
m=mass
m*g*sin(24) = ma(at slope direction)
divide both side by m
we got
g*sin(24)=a

then use
v^2(final) = V^2(initial)+2(9.8m/s^2)(sin(24))(1300m)
V^2(final) = 0+2(9.8m/s^2)(sin(24))(1300m) we know that initial v is zero.
we get V from the equation above.
then use
v= v(initial)+at
v=0+(9.8m/s^2)sin(24)t
t=V/9.8sin(24).
done!

 

[Mindscrape]

I suppose it would be okay, but why not just use

$$s(t) = s_0 + v_0t +\frac{1}{2}at^2$$

and solve for t?

Did you mean a 24 degree slope, or are you putting in the wrong angle?

 

[Moetasim]

Your attempt at solving the problem seems correct. You correctly identified the forces acting on the skier (gravity and normal force) and used Newton's second law to solve for the acceleration. You then used the kinematic equations to solve for the final velocity and then the time it takes to reach the bottom of the slope. However, it would be helpful to include units in your calculations and to clearly state your final answer in the correct units (seconds). Also, make sure to double check your calculations to ensure accuracy. Overall, good job on solving the problem!