Question: 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 center of gravity when she sits on one end of the board. How far is she from the support point? (0.67 m)
Answer Options:
0.67 m
1.0 m
2.0 m
4.0 m
Answer: 0.67 m
Question: 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. (170 N)
Answer Options:
50 N
100 N
170 N
200 N
Answer: 170 N
Question: 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? (30 cm)
Answer Options:
20 cm
30 cm
40 cm
50 cm
Answer: 30 cm
Question: An 800-N billboard worker stands on a 4.0-m scaffold weighing 500 N and supported by vertical ropes at each end. How far would the worker stand from one of the supporting ropes to produce a tension of 550 N in that rope? (2.5 m)
Answer Options:
1.0 m
2.0 m
2.5 m
3.0 m
Answer: 2.5 m
Question: A uniform bridge span weighs 50.0 x 10³ N and is 40.0 m long. An automobile weighing 15.0 x 10³ N is parked with its center of gravity located 12.0 m from the right pier. What upward support force does the left pier provide? (29.5 x 10³ N)
Answer Options:
20 x 10³ N
25 x 10³ N
29.5 x 10³ N
35 x 10³ N
Answer: 29.5 x 10³ N
Question: A uniform 1.0-N meter stick is suspended horizontally by vertical strings attached at each end. A 2.0-N weight is suspended from the 10-cm position on the stick, another 2.0-N weight is suspended from the 50-cm position, and a 3.0-N weight is suspended from the 60-cm position. What is the tension in the string attached at the 100-cm end of the stick? (3.5 N)
Answer Options:
2.0 N
2.5 N
3.0 N
3.5 N
Answer: 3.5 N
Question: Masses are distributed in the x,y-plane as follows: 6.0 kg at (0.0, 0.0) m, 4.0 kg at (2.0, 0.0) m, and 5.0 kg at (2.0, 3.0) m. What is the x-coordinate of the center of gravity of this system of masses? (1.2 m)
Answer Options:
1.0 m
1.2 m
1.5 m
2.0 m
Answer: 1.2 m
Question: Masses are distributed in the xy-plane as follows: 10 kg at (2.0, 6.0) m, 4.0 kg at (2.0, 0.0) m, and 6.0 kg at (0.0, 3.0) m. Where would a 20-kg mass need to be positioned so that the center of gravity of the resulting four mass system would be at the origin? (-1.4m, -3.9m)
Answer Options:
(0, 0)
(-1.4m, -3.9m)
(1.4m, 3.9m)
(2.0m, 6.0m)
Answer: (-1.4m, -3.9m)
Question: A hoop of radius 1.0 m is placed in the first quadrant of a xy-coordinate system with its rim touching both the x-axis and the y-axis. What are the coordinates of its center of gravity? (1.0m, 1.0m)
Answer Options:
(0, 0)
(1.0m, 1.0m)
(2.0m, 2.0m)
(1.5m, 1.5m)
Answer: (1.0m, 1.0m)
Chapter 9
Question: A copper wire of length 2.0 m, cross-sectional area 7.1 x 10⁻⁶ m² and Young’s modulus 11 x 10¹⁰ N/m² has a 200-kg load hung on it. What is its increase in length? (5.0 mm)
Answer Options:
2.0 mm
3.5 mm
5.0 mm
7.0 mm
Answer: 5.0 mm
Question: A uniform pressure of 7.0 x 10⁵ N/m² is applied to all six sides of a copper cube. What is the percentage change in volume of the cube? (for copper, B = 14 x 10¹⁰ N/m²) (0.5 x 10⁻³ %)
Answer Options:
0.2 x 10⁻³ %
0.5 x 10⁻³ %
1.0 x 10⁻³ %
1.5 x 10⁻³ %
Answer: 0.5 x 10⁻³ %
Question: Consider two steel rods, A and B. B has three times the area and twice the length of A, so Young’s modulus for B will be what factor times Young’s modulus for A? (1.0)
Answer Options:
1.0
2.0
3.0
4.0
Answer: 1.0
Question: How large a force is necessary to stretch a 2.0-mm-diameter steel wire (Y = 2.0 x 10¹¹ N/m²) by 1.0%? (6.3 x 10³ N)
Answer Options:
2.0 x 10³ N
4.0 x 10³ N
6.3 x 10³ N
8.0 x 10³ N
Answer: 6.3 x 10³ N
Question: What is the total force on the bottom of a 2.0-m-diameter by 1.0-m-deep round wading pool due to the weight of the air and the weight of the water? (1 atmosphere = 1.0 x 10⁵ N/m²) (3.4 x 10⁵ N)
Answer Options:
2.0 x 10⁵ N
3.4 x 10⁵ N
4.8 x 10⁵ N
6.0 x 10⁵ N
Answer: 3.4 x 10⁵ N
Question: A piece of aluminum has density 2.70 g/cm³ and mass 775 g. The aluminum is submerged in a container of oil of density 0.650 g/cm³. A spring balance is attached with string to the piece of aluminum. What reading will the balance register in grams (g) for the submerged metal? (588 g)
Answer Options:
500 g
588 g
700 g
800 g
Answer: 588 g
Question: A block of wood has density 0.50 g/cm³ and mass 1 500 g. It floats in a container of oil (the oil’s density is 0.75 g/cm³). What volume of oil does the wood displace? (2 000 cm³)
Answer Options:
1 500 cm³
2 000 cm³
2 500 cm³
3 000 cm³
Answer: 2 000 cm³