Exam 8: Equilibrium and Elasticity

A uniform sign is supported at P as shown in the figure.If the sign is a square 0.7 m on its side and its mass is 7.0 kg,what is the magnitude of the horizontal force that P experiences?

In the figure,the Achilles tendon exerts a force F = 720 N.What is the torque it exerts about the ankle joint?

If two forces of equal magnitude act on an object that is hinged at a pivot,the force acting farther from the pivot must produce the greater torque about the pivot.

Which of the following is an accurate statement?

The figure shows two forces acting on an object.They have magnitudes F₁ = 9.6 N and F₂ = 3.2 N.What third force will cause the object to be in equilibrium?

A steel wire,3.2 m long,has a diameter of 1.2 mm.The wire stretches 1.6 mm when it bears a load.Young's modulus for steel is 2.0 x 1011 n/m².The mass of the load is closest to:

A car is being towed at constant velocity on a horizontal road using a horizontal chain.The tension in the chain must be equal to the weight of the car in order to maintain constant velocity.

A spring stretches by 21.0 cm when a 135 N object is attached.What is the weight of a fish that would stretch the spring by 44.9 cm?

-A 50 kg uniform ladder,5.0 m long,is placed against a smooth wall at a height of h = 3.7 m.The base of the ladder rests on a rough horizontal surface whose coefficient of static friction is 0.40.An 80 kg block is suspended from the top rung of the ladder,just at the wall.In the figure,the magnitude of the force exerted on the base of the ladder,due to contact with the rough horizontal surface is closest to:

-A 100 kg nonuniform boom,6.0 m long,is loosely pinned at the pivot at P.A 700 kg block is suspended from the end of the boom at A.The boom forms a 30° angle with the horizontal,and is supported by a cable,4.0 m long,between points D and B.Point B is 4.0 m from P,and point D is 4.0 m above P.The center of mass of the boom is at point C,which is 2.0 m from P.In the figure,the y-component of the pivot force on the boom at P is closest to:

-In the figure,a certain type of string will break if the tension in the string exceeds 300 N.A number of 8-kg weights are hung one below the other from a hook in the ceiling using this string.The number of weights that causes the string to break and the string segment that will break are as follows:

Two blocks,A and B,are being pulled to the right along a horizontal surface by a horizontal 100 N pull,as shown in the figure.Both of them are moving together at a constant velocity of 2.0 m/s to the right,and both weigh the same.Which of the figures below shows a correct free-body diagram of the horizontal forces acting on lower block,B?

An irregularly shaped object 10 m long is placed with each end on a scale.If the scale on the right reads 74 N and the scale on the left reads 93 N,how far from the left is the center of gravity?

A 20 kg uniform door has a width of 1.2 m and a height of 2.5 m. The door is mounted on a post by a pair of hinges, marked 1 and 2, at the top and bottom of the door. An external force of 60 N, at an angle of 30° above the horizontal, is applied to the doorknob, as shown. The doorknob is 1.0 m above the bottom of the door. -In the figure,the x-component of the force,exerted on the door at the top by hinge 1,is closest to:

-In the figure,a ladder of weight 200 N and length 10 meters leans against a smooth wall (no friction on wall).A firefighter of weight 600 N climbs a distance x up the ladder.The coefficient of friction between the ladder and the floor is 0.5.What is the maximum value of x if the ladder is not to slip?

A uniform 1200 N beam that is 3.50 m long is suspended horizontally by two vertical wires at its ends.A small but dense 550 N weight is placed on the beam 2.00 m from one end,as shown in the figure.The tensions,A and B,in the two wires are:

A 20 kg uniform door has a width of 1.2 m and a height of 2.5 m. The door is mounted on a post by a pair of hinges, marked 1 and 2, at the top and bottom of the door. An external force of 60 N, at an angle of 30° above the horizontal, is applied to the doorknob, as shown. The doorknob is 1.0 m above the bottom of the door. -In the figure,the x-component of the force,exerted on the door at the bottom by hinge 2,is closest to:

-A 100 kg nonuniform boom,6.0 m long,is loosely pinned at the pivot at P.A 600 kg block is suspended from the end of the boom at A.The boom forms a 30° angle with the horizontal,and is supported by a cable,4.0 m long,between points D and B.Point B is 4.0 m from P,and point D is 4.0 m above P.The center of mass of the boom is at point C,which is 2.0 m from P.In the figure,the tension in the cable is closest to:

-In the figure,what mass M is required to balance the mobile?

A 20 kg uniform door has a width of 1.2 m and a height of 2.5 m. The door is mounted on a post by a pair of hinges, marked 1 and 2, at the top and bottom of the door. An external force of 60 N, at an angle of 30° above the horizontal, is applied to the doorknob, as shown. The doorknob is 1.0 m above the bottom of the door. -In the figure,the sum of the y-components of the forces,exerted on the door by hinges 1 and 2,is closest to: