Exam 8: Equilibrium and Elasticity

-A uniform 600 kg beam,6 m long,is freely pivoted at P.The beam is supported in a horizontal position by a light strut,5 m long,which is freely pivoted at Q and is loosely pinned to the beam at R.A load of mass is suspended from the end of the beam at S.A maximum compression of 18,000 N in the strut is permitted,due to safety.In the figure,under maximum load,the x-component of the force exerted on the beam by the pivot at P is closest to:

-In the figure,a block of mass M hangs in equilibrium.The rope that is fastened to the wall is horizontal and has a tension of 38 N.The rope that is fastened to the ceiling has a tension of 59 N and makes an angle Θ with the ceiling.The angle Θ is:

-A 40 kg uniform ladder,5.0 m long,is placed against a smooth wall at a height of h = 4.0 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 force exerted on the wall by the ladder is closest to:

A box of mass m is pulled with a constant acceleration a along a horizontal frictionless floor by a wire that makes an angle of 15 degrees above the horizontal.The tension in this wire is greater than ma.

-A uniform 600 kg beam,6 m long,is freely pivoted at P.The beam is supported in a horizontal position by a light strut,5 m long,which is freely pivoted at Q and is loosely pinned to the beam at R.A load of mass is suspended from the end of the beam at S.A maximum compression of 25,000 N in the strut is permitted,due to safety.In the figure,under maximum load the y-component of the force exerted on the beam by the pivot at P is closest to:

Do all points on a rigid,rotating body have the same angular acceleration? Support your answer.

An object attached to a spring is pulled across a frictionless surface.If the spring constant is 45 N/m and the spring is stretched by 0.88 m when the object is accelerating at 1.4 m/s2,what is the mass of the object?

A force of 30 N stretches a spring 0.73 m from equilibrium.What is the value of the spring constant?

A stone rolls down a sloping hillside.The normal force that the surface of the hill exerts on the stone is equal to the stone's weight.

Three forces A, B, and C act on a body as shown. A fourth force F is required to keep the body in equilibrium. -In the figure,the x-component of force F is closest to:

Two unequal weights are connected by a massless string which passes over a frictionless pulley.If the pulley has no appreciable mass,the tension in the string is the same on both sides of the pulley;but if the pulley has mass,the tension will not be the same on both sides of the pulley.

If the forces on an object balance,it does not necessarily follow that the torques balance.

A winch is being used to raise a 100 N load.If the motor supplies a torque at a radius of 1.4 m and the cylinder upon which the rope is being wrapped has a radius a 0.6 m,how much force must the motor supply to keep the load suspended in place while the work crew goes to lunch?

A man pushes against a rigid,immovable wall.Which of the following is the most accurate statement concerning this situation?

A small branch is wedged under a rock and rests on a smaller object.The smaller object is 2.0 m from the large rock and the branch is 10.0 m long.If the mass of the branch is 20.0 kg what force must be exerted on the smaller rock?

Suppose that a heavy person and a light person are balanced on a teeter-totter made of a plank of wood.Each person now moves in toward the fulcrum a distance of 25 cm.What effect will this have on the balance of the teeter-totter?

Three forces A, B, and C act on a body as shown. A fourth force F is required to keep the body in equilibrium. -In the figure,the y-component of force F is closest to:

-A uniform 200 kg beam,6 m long,is freely pivoted at P.The beam is supported in a horizontal position by a light strut,5 m long,which is freely pivoted at Q and is loosely pinned to the beam at R.A load of mass is suspended from the end of the beam at S.A maximum compression of 25,000 N in the strut is permitted,due to safety.In the figure,the maximum mass M of the load is closest to:

-A 500 kg nonuniform boom,6.0 m long,is loosely pinned at the pivot at P.A 800 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 X-component of the pivot force on the boom at P is closest to: