Question

After a hard day's work, you return home and decide to clean your apartment. In order to do so, you need to move your bed which has a mass of 110 kg. You exert a horizontal force of 270 N and your bed refuses to move. You roll up your sleeves and keep pushing until you exert a horizontal force 540 N. The bed slides a little but now you are exhausted and stop pushing. You have an aha! moment as you recall what you learned in Physics 101. Consequently, you remove the bed's mattress (21 kg) and push the bed again with the same horizontal force as before. This time the bed slides with an acceleration of 1.65 m/s^2. In the first answer box, enter the co-efficient of static friction between the bed and the floor. In the second answer box, enter the co-efficient of kinetic friction between the bed and the floor.

Answer 1

mass of Bed with mattress Mbm= 110 kg

mass of Mattress Mm = 21 kg

mass of bed without mattress Mb = 110-21 = 99kg

Force required to move Bed with mattress = 540 N

normal reaction of bed N= Mbm*g = 110*9.8 = 1078 N

coefficient of static friction Ks = 1078/540 = 0.5

normal reaction of bed without mattress = Mb*g = 99*9.8

acceleration a = 1.65 m/s^2

Force on the bed = 99*1.65

let Kk is kienetic friction co-efficient

the we will have

99*1.65 = 99*9.8*Kk

co-effiecient ofkienetic friction Kk = 1.65/9.8 = 0.17