2a. A professor holds an eraser against a vertical chalkboard bypushing horizont

Question

2a. A professor holds an eraser against a vertical chalkboard bypushing horizontally on it. He pushes with a force that is muchgreater than is required to hold the eraser. The force of frictionexerted by the board on the eraser increases if he: pushes withslightly less force
pushes so his forceis slightly downward but has the same magnitude
pushes so his forceis slightly upward but has the same magnitude
pushes withslightly greater force
stops pushing 2b. If a certain car, going with speed v1, rounds a level curvewith a radius R1, it is just on the verge of skidding. If its speedis now doubled, the radius of the tightest curve on the same roadthat it can round without skidding is: R1/2
R1/4
2R1
R1
4R1 Pls kindly explain ur answers, Thanks!

Explanation / Answer

2a) pushes with slightly greater force Force of professor = Normal force board exerts on eraser Friction force = *Normal force, where is acoefficient of friction. As normal force goes up, so does friction force 2b) v12/r1 =v22/r2 = acceleration v2 = 2v1 v12/r1 =(2v1)2/r2 =4v12/r2 r2 = 4*r1

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