Moments (AQA AS Physics)

A force of 9.8 N is applied at one end of a uniform beam of mass 2 kg that balances in equilibrium.

Which of the following corresponds to the correct value of the reaction R on the beam?

A load L of 5000 N is placed on a horizontal beam between two boxes A and B. The beam itself exerts a force of 10 kN at its centre of mass.

The two reaction forces from the boxes are R₁ and R₂.

Which of the following corresponds to the correct value of R₁?

The uniform bar of length 0.60 m has a weight of 12 N and is in equilibrium in the diagram below. There is a hinge on the far right of the bar.

What is the reading on the Newtonmeter?

The wall hook shown has a weight of 50 N attached to the end.

What is the moment on the point of attachment to the base?

A door handle in the diagram below has a length 10 cm requires a force of 20 N to turn it.

If the handle breaks and the door must be opened using the axle of the handle, with a diameter of 0.5 cm, how much force is needed?

A load L is placed on a horizontal beam balanced by boxes A and B. The beam has a mass mg.

If load L is moved from box A towards box B, which of the following statements is true?

A car bonnet, represented by QP, of mass 12 kg is pivoted at P. Its weight acts at G where QG = GP = 2.0 m.

What force, F, acting perpendicular to QP as shown, is required to hold the bonnet at 40° to the horizontal?

A car wheel nut can be loosened by applying a force of 310 N on the end of a bar of length 0.7 m as in X. A car mechanic is capable of applying forces of 650 N simultaneously in opposite directions on the ends of a wheel wrench as in Y.

What is the minimum length l of the wrench which would be needed for him to loosen the nut?

The diagram shows a uniform beam of weight 2.5 N and length of 150 cm is pivoted 32 cm from one end for use as a simple balance.

A rock is placed at the end of the beam. The beam moves to a steady horizontal position when a weight of 7.1 N is added at a distance of 80 cm from the pivot as shown.

What is the weight of the rock?

An object, made from two equal masses joined by a light rod, falls with uniform speed through air. The rod remains horizontal.

Which statement about this system is incorrect?

The diagram shows a uniform shelf along the axis XY with a mass 0.5 kg. A 3 kg load is placed at Y and a wire of tension T holds the shelf to the wall.

What is the magnitude of the tension in the supporting wire?

The wedge shown in the diagram below is suspended in equilibrium by a cable at an angle of 120º to the longest part.

The wedge has a mass of 200 kg, with a centre of mass ¾ of the length of AB from the hinge at A. AB is 2 m long and BC is 1.2 m high.

What is the tension on the cable?

The medieval war machine shown below launches a stone projectile when the cable is released.

What is the tension T in the cable in the position shown?

The diagram below represents the arm of a crane lifting a 100 kN load. The arm has a mass of 8000 kg and a machine produces a reaction force F of 5 m from the bottom of the arm. The crane arm is uniform and in equilibrium.

What is the value of F?

The diagram below shows an irregular object supported on two springs. The spring on the left has a spring constant of k₁ and a load of 20 N acts 0.50 m from this spring and 0.25 m from the spring on the right.

When the object is placed on the bottom of the springs, they each extend by the same amount.

If the object is to be horizontal, what is the value of the spring constant for the spring on the right?

A triangular object with a base diameter of 1m below is to be tilted until it falls over. The arrow drawn is the point at which the centre of mass of the cone acts.

What height will the highest point on the base be just before the object falls over?

A car is driving up a uniform beam, of length 12 m. The car has a mass of 1000 kg and the beam has a mass of 200 kg. 

How far along the beam beyond the pivot point can the car go just before the beam topples?

The diagram shows a child’s balancing game.

The wooden rod is uniform and all the rings are of equal mass. Two rings are hung on peg 14, one on peg 2 and one on peg 11.

On which hook must a fourth ring be hung in order to balance the rod?

A uniform rod with a rubber handle and wooden section is made to balance on a pivot as shown below.

What is the ratio  ?

The diagram below four tangential forces applies to a circular object with radius r.

If the clockwise direction is taken as positive, what is the resultant moment acting on the object?