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Practice Questions

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This activity contains 25 questions.

Question 1.
What condition or conditions are necessary for rotational equilibrium?


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Question 2.
What condition or conditions are necessary for translational equilibrium?


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Question 3.

A heavy seesaw is out of balance. A lightweight girl sits on the end that is tilted downward, and a heavy boy sits on the other side so that the seesaw now balances. If the boy and girl both move forward so that they are one-half their original distance from the pivot point, what will happen to the seesaw?

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Question 4.

A force is applied to the end of a 2 m long uniform board weighing 50 N in order to keep it horizontal, while it pushes against a wall at the left. If the angle the force makes with the board is 30° in the direction shown, the applied force F is


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Question 5.
A force is applied to the end of a 2 m long uniform board weighing 50 N in order to keep it horizontal, while it pushes against a wall at the left. What is the horizontal component of the wall force?


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Question 6.

A uniform rod has a weight of 40 N and a length of 1 m. It is hinged to a wall (at the left end), and held in a horizontal position by a vertical massless string (at the right end). What is the magnitude of the torque exerted by the string about a horizontal axis which passes through the hinge and is perpendicular to the rod?


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Question 7.

A uniform rod has a weight of 40 N and a length of 1 m. It is hinged to a wall (at the left end), and held in a horizontal position by a vertical massless string (at the right end). What is the force in the string in the previous question?


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Question 8.

A uniform rod has a weight of 40 N and a length of 1 m. It is hinged to a wall (at the left end), and held in a horizontal position by a vertical massless string (at the right end). What is the magnitude of the hinge force?


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Question 9.

A uniform rod has a weight of 40 N and a length of 1 m. It is hinged to a wall (at the left end), and held in a horizontal position by a vertical massless string (at the right end). If the string is let go, what will be the initial angular acceleration?


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Question 10.
In the figure below, five forces act on a massless rod free to pivot at Point P. Which force is producing a counter-clockwise torque about Point P?


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Question 11.

The slope of the straight line shown on the graph is called the


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Question 12.

Region A in the above figure is called the


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Question 13.

The Region B in the figure in the previous limit is called the


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Question 14.

The Point C in the figure is clearly not the


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Question 15.

The Point D in the figure is called the


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Question 16.

A person with a mass of 80 kg hangs from a trapeze suspended by two elastic cords. The force-stretch properties of the cords are shown in the figure. How far do the cords stretch?


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Question 17.

A person with a mass of 80 kg hangs from a trapeze suspended by two elastic cords. The force-stretch properties of the cords are shown in the figure. If the cords are 10 meters long and made of Nylon (E = 5 x 109 N/m2), what is their diameter?


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Question 18.

A person with a mass of 80 kg hangs from a trapeze suspended by two elastic cords. The force-stretch properties of the cords are shown in the figure. If the nylon cords have a radius of 6 mm, what is their length?


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Question 19.

A person with a mass of 80 kg hangs from a trapeze suspended by two elastic cords. The force-stretch properties of the cords are shown in the figure. If a cord described by the figure has a cross sectional area of .79 square centimeters and is stretched a half of a centimeter when a certain force is applied, what is the stress on it?


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Question 20.

The red circle in the above 'movie' represents a person on a ladder. In which frame is the force of friction between the ladder and the ground the least? (There is no friction with the wall.)


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Question 21.

The red circle in the above 'movie' represents a person on a ladder. At which points is the ladder most in danger of falling?


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Question 22.

The red circle in the above 'movie' represents a person on a ladder. When is the wall force equal in magnitude to the force of friction?


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Question 23.

The red circle in the above 'movie' represents a person on a ladder. When is the normal force from the ground a minimum?


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Question 24.

The bottom of the ladder is 1.2 m from the wall. What is the magnitude of the torque from the wall force about an axis through the bottom of the ladder?


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Question 25.

The bottom of the ladder is 1.2 m from the wall. What is the magnitude of the torque from the red weight 1/3 of the way up the ladder about an axis through the bottom of the ladder?


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