Question

1. A block sits on a ramp whose angle can vary. You slowly tilt the ramp, increasing the angle, until the block starts to slip when the angle is 32.0^o. What is the coefficient of static friction?

2. When you stand on a scale at rest, it reads 59 kg. However, your friend notices that the scale reads 66 kg when you push off to jump upwards on the scale.. What is the upward acceleration of your center of mass at this time? Answer in m/s². Note your center of mass is accelerating upwards but your feet are still contact with the scale.

Use the free body diagram method and remember that the scale actually reads the normal force divided by g.

Use g=9.8 m/s² if you need g.

Answer 1

Question 1 is the case of , angle of repose, Angle of repose means the angle of inclination of inclined at which a body on it just tends move or start to move. At angle of repose maximum static force of friction acts which is called limiting force of friction. Q2 is similar to case of apparent weight, when you starts off to jump from scale you need force equal to ma where m is your actual mass and a is your acceleration to jump hence , now your weight is w' = m(g+a) that cause increasmnent of your mass as shown by scale. we have to find acceleration. see the attached image.