An elevator weighing 20 000 N is supported by a steel cable. What is the tension in the cable when the elevator is being accelerated upward at a rate of 3.00 m/s2? (g = 9.80 m/s2)
a. 6.1E+3 N
b. 2.0E+4 N
c. 6.0E+4 N
d. 2.6E+4 N
e. 6.7E+3 N
[Ques. 2] A 14-kg block rests on a level frictionless surface and is attached by a light string to a 5.0-kg hanging mass where the string passes over a massless frictionless pulley. If g = 9.8 m/s2, what is the tension in the connecting string?
a. 2.6 N
b. 21 N
c. 49 N
d. 36 N
e. 190 N
[Ques. 3] Two blocks of masses 20 kg and 9.0 kg are connected together by a light string and rest on a frictionless level surface. Attached to the 9.0-kg mass is another light string, which a person uses to pull both blocks horizontally. If the two-block system accelerates at 0.80 m/s2, what is the tension in the second string attached to the 9.0-kg mass?
a. 23 N
b. 14 N
c. 16 N
d. 7.2 N
e. 25 N
[Ques. 4] Two blocks of masses 30.0 kg and 8.0 kg are connected together by a light string and rest on a frictionless level surface. Attached to the 8.0-kg mass is another light string, which a person uses to pull both blocks horizontally. If the two-block system accelerates at 0.60 m/s2 what is the tension in the connecting string between the blocks?
a. 23 N
b. 37 N
c. 18 N
d. 4.8 N
e. 50 N
[Ques. 5] Two blocks, joined by a string, have masses of 3.0 and 4.0 kg. They rest on a frictionless horizontal surface. A second string, attached only to the 4.0-kg block, has horizontal force = 40 N applied to it. Both blocks accelerate. Find the tension in the string between the blocks.
a. 23 N
b. 5.7 N
c. 17 N
d. 93 N
e. 120 N
[Ques. 6] A box slides up an incline with an angle of elevation . When the box reaches its maximum distance up the incline it stops and does not slide down the incline due to friction. What is the minimum value of the coefficient of static friction for this to occur?
a. s = tan b. s = sin
c. s = cos d. s = 1
[Ques. 7] Which is the correct expression for the force of static friction, where n is the normal force?
a. fs < sn
b. fs sn
c. fs > sn
d. fs sn
[Ques. 8] A sled is on a horizontal surface and a rope with tension T is pulling on it at an angle above the horizontal. The sled had mass M and does not move due to the frictional force. In this case the coefficient of friction is s. In terms of the variables given and g, what is the magnitude of the frictional force in this case?
a. sMg b. Tcos
c. Tsin d. sMgcos
[Ques. 9] A box of mass m is placed on an incline with angle of inclination . The box does not slide. The magnitude of the frictional force in this case is:
a. s mg sin .
b. mg cos .
c. mg sin .
d. not given.
[Ques. 10] A box is to be moved across a level surface. A force of magnitude 200 N may be applied at an angle of 30 below the horizontal to push the box or at an angle of 30 above the horizontal to pull the box, either application sufficient to overcome friction and move the box. Which application will cause the box to have the greater acceleration?
a. the one below the horizontal
b. the one above the horizontal
c. both give equal acceleration
d. more information is needed
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