# Mass of an Object Moving Down a Slope.

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1. Nov 6, 2015

### Cailan Emmett

Hello,

I am trying to find the magnitude of the resistance force of an object moving down a slope.
The question I was given says:
A skateboarder heads down a gentle slope (Θ=5°) at a constant speed of 5m/s. Calculate the magnitude of the resistance force.
Using the equation mgSinΘ - ma = R, (g = 9.8, a = 0) I got as far as m0.854 = R, but I need m to find R.
Is there another equation to find m (the mass of the object)?

Any help would be much appreciated.

2. Nov 6, 2015

What is R?

3. Nov 6, 2015

### Cailan Emmett

R is the resistance force on the object (friction, air resistance etc.).

Basically the forces going in the opposite direction to the skateboard.

4. Nov 6, 2015

### Coolcatss

Distance, Height? Anything else given to you?

5. Nov 6, 2015

### Cailan Emmett

Unfortunately no. Only the angle of elevation and speed of the object.

6. Nov 6, 2015

### Staff: Mentor

Ah, ok. Then, if you're not given the mass of the object, $mg \sin \theta$ is the best you can do.

7. Nov 7, 2015