a 60.0 lb block rests on a smooth plane at an angle of 20 degrees with the horizontal. The block is pulles up the plane with a force of 30.0 lb parallel to the plane. What is its acceleration?

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anonymous · Answer

is there anyone who can answer this? please help me

anonymous · Answer

Assuming both lb quantities are pound-force, then this is a simple balance of forces. 

Keep in mind that the weight of the block acts directly downward. We need to resolve this weight into (1) Normal component and (2) Tangential component relative to the inclined plane. The tangential component is of interest to us because this acts "in-line" or parallel to the 30 lb force. $${w_b \over g} \cdot \vec a = F_{applied} - F_{tangential}$$where $w_b$ is the given weight of the block, $\vec a$ is the acceleration of the block along the inclined plane, $F_{applied}$ is the given applied force, and $F_{tangential}$ is the tangential component of the block's weight to the inclined plane.