Calculate Total Upward Force Skateboard Mass 65kg, Half Pipe 3m

[Masafi]

skateboard mass = 65kg

he skates down on a half pipe, radius = 3m

If he is traveling at 3.6 m/s when at bottom of ht hallf pipe, what will be the total upward force?

Is this basically the centripetal force + the reaction to the weight?

i.e. centripetal force + mg?

 

[Doc Al]

The phrase 'total upward force' is a bit ambiguous, as is the term 'reaction to the weight'. Presumably you want the upward force that the surface exerts on the skater (usually called the 'normal force', N).

If so, you have the right answer. But a simpler way to understand it is to apply Newton's 2nd law:
ΣF = ma
N - mg = ma_c
Thus: N = ma_c + mg

 

[kerimek]

I would say that your understanding is correct. The total upward force on the skateboarder can be calculated by adding the centripetal force (which is responsible for keeping the skateboarder moving along the curved path of the half pipe) and the reaction force to the weight of the skateboarder (which is equal to the weight of the skateboarder in this case). The formula for calculating the centripetal force is Fc = mv^2/r, where m is the mass of the skateboarder, v is the velocity, and r is the radius of the half pipe. Therefore, the total upward force can be calculated as Ftotal = Fc + mg = (65kg)(3.6m/s)^2/3m + (65kg)(9.8m/s^2) = 257.6N + 637N = 894.6N. This means that the total upward force on the skateboarder is about 895 Newtons, which is the combined force of the centripetal force and the reaction force to the weight.