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Question :
11. Tasha has mass 20 kg and wants to use : 2102168

11. Tasha has mass 20 kg and wants to use a 4.0-m board of mass 10 kg as a seesaw. Her friends are busy, so Tasha seesaws by herself by putting the support at the system's center of gravity when she sits on one end of the board. How far is she from the support point?

A. 2.0 m

B. 1.0 m

C. 0.67 m

D. 0.33 m

12. An 80-kg man is one fourth of the way up a 10-m ladder that is resting against a smooth, frictionless wall. If the ladder has a mass of 20 kg and it makes an angle of 60? with the ground, find the force of friction of the ground on the foot of the ladder.

A. 7.8 ´ 10^{2} N

B. 2.0 ´ 10^{2} N

C. 50 N

D. 1.7 ´ 10^{2} N

13. A 100-N uniform ladder, 8.0 m long, rests against a smooth vertical wall. The coefficient of static friction between ladder and floor is 0.40. What minimum angle can the ladder make with the floor before it slips?

A. 22?

B. 51?

C. 18?

D. 42?

14. A meter stick is supported by a knife-edge at the 50-cm mark. Doug hangs masses of 0.40 and 0.60 kg from the 20-cm and 80-cm marks, respectively. Where should Doug hang a third mass of 0.30 kg to keep the stick balanced?

A. 20 cm

B. 70 cm

C. 30 cm

D. 25 cm

15. An 800-N billboard worker stands on a 4.0-m scaffold supported by vertical ropes at each end. If the scaffold weighs 500 N and the worker stands 1.0 m from one end, what is the tension in the rope nearest the worker?

A. 450 N

B. 500 N

C. 800 N

D. 850 N