PRACTICE / Static friction

Find friction before the block slips.

A 2 kg block rests on a fixed plane inclined at 30° to the horizontal. The coefficient of static friction is 0.8. Take g = 10 m/s².

What is the static friction force on the block?

1. A$8\sqrt3\ \mathrm N\ \text{up the plane}$
2. B$10\ \mathrm N\ \text{down the plane}$
3. C$20\ \mathrm N\ \text{up the plane}$
4. D$10\ \mathrm N\ \text{up the plane}$

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