54 ldee case Rigid body In realia figure 3 . It our simplified model of forces,

Question

54 ldee case Rigid body In realia figure 3 . It our simplified model of forces, it can be difficult to see why rolling friction exists. Rolling friction exists because all matter deforms by some amount when pushed on. This deformation causes resistive forces while objects roll as in Figure 3. Using this idea, come up with an example of something that would have a very high coefficient of rolling friction and something that would have a very low coefficient of rolling friction. Explain why/how your examples work. Practice Problem A mass of 2kg is at rest on a ramp making an angle of ? 20° with the ground as drawn. A force of 3N also acts on the mass, gently nudging the mass downward, parallel to ramp's surface. If the coefficient of static friction between the ramp and mass is As 0.6, what is the force of stotic friction in this case? (Incorrect Answers: 11.76N, 11.05N)

Explanation / Answer

Normal force acting on the block, N = m*g*cos(theta)

= 2*9.8*cos(20)

= 18.4 N

Maximum Force of static friction, Fs_max = mue_s*N

= 0.6*18.4

= 11.05 N

force acting towards down = m*g*sin(theta) + F

= 2*9.8*sin(20) + 3

= 9.70 N

As the block is not moving, Fnet = 0

9.7 - Fs = 0

Fs = 9.70 N <<<<<<------------------Answer

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