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Geometry of object

Started by SaintJude
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SaintJude

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Consider 2 objects of equal mass, center of gravity, same initial velocity, and same us and uk. Both objects are sitting at the top on an inclined plane. One is a ball & one is a block. If both object have same contact surface area, which would hit the ground first.

It's the Ball!?! Why? The explanation tells me to use my intuition, but my intuition say fk = u* normal force...

Apparently, the geometry of the ball will be such that "while friction causes the block to slow down, the direction of the friction actually helps the ball to roll." Still doesn't make entire sense
 
Rolling objects do not lose as much energy via friction. The frictional force causes rotation, which is an additional source of KE to get the ball to the bottom faster.

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