3. Exercises

A sphere, of mass 20 kg, is supported by a single vertical cable. Find the tension in the cable.

A sphere, of mass 20 kg, is supported by a single vertical cable. Find the tension in the cable.

The diagram shows two masses and two strings that are suspended from a fixed point. Find the tension in each string.

A plank leans against the back of a lorry, as shown in the diagram. Draw a diagram to show the forces acting on the plank.

Two books are placed, one on top of each other on a horizontal surface. The top book has mass 1.2 kg and the lower book has mass 1.8 kg.

a) Draw diagrams to show the forces on each book.

b) Calculate the magnitude of the normal reaction force acting on the top book.

c) Calculate the magnitude of the normal reaction forces acting on the bottom book.

A simple pendulum consists of a small metal sphere attached to a length of string. The sphere then swings in a vertical plane, describing a circular arc. Draw a diagram to show the forces acting on the sphere when it is at

a) its lowest point,

b) its highest point,

c) between its highest and lowest points.

A sledge slides down a slope. Draw a diagram to show the forces acting on the sledge.

Three boxes have masses of 5 kg, 12 kg and 10 kg. They are stacked on a horizontal surface with the 12 kg box at the bottom. Draw a diagram to show the forces acting on this box and calculate the magnitude of each of these forces.

A box, of mass 200 kg, is on a rough, horizontal surface. A horizontal force of magnitude P N acts on the box as shown in the diagram. The coefficient of friction between the surface and the box is 0.4.

(a) Calculate the magnitude of the normal reaction force acting on the box.

b) What is the magnitude of the friction force on the box if \displaystyle P=760\text{ N}.

Explain your answer.

c) Calculate the magnitude of the resultant force on the box if \displaystyle P=1000\text{ N}.