# Mass and Kinetic Friction

Fig. 6-31

A)150 NB)175 NC)125 ND)200 N

2) In Fig. 6-33, two blocks are connected over a pulley. The mass of block A is 7.8 kg and the coefficient of kinetic friction between A and the incline is 0.13. Angle θ of the incline is 44°. Block A slides down the incline at constant speed. What is the mass of block B?

Fig. 6-33

A)4.69gB)5.69gC)5.0gD)6.0g

3) In the figure here, block 1 of mass 2.0 kg and block 2 of mass 2.9 kg are connected by a string of negligible mass and are initially held in place. Block 2 is on a frictionless surface tilted at θ = 20 ˚. The coefficient of kinetic friction between block 1 and the horizontal surface is 0.28. The pulley has negligible mass and friction. Once they are released, the blocks move. What then is the tension in the string?

A)7.2 NB)8.2 NC)9.2 ND)10.2 N

4) A wheel has a constant angular acceleration of 2.5 rad/s2. During a certain 5.0 s interval, it turns through an angle of 67 rad. Assuming that the wheel started from rest, how long had it been in motion before the start of the 5.0 s interval? A)3.86 sB)4.86 sC)2.86 sD)6.86

5) A diver makes 2.5 revolutions on the way from a 8.5-m-high platform to the water. Assuming zero initial vertical velocity, find the diver's average angular velocity during a dive. A)11.99 rad/sB)10.00 rad/sC)100.00 rad/sD)10.99 rad/s

Answer key

1) C

2) A

3) A

4) C

5) A

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