Worked examples A car of mass 1000 kg travelling at 36 km/h is brought to rest over a distance of 20 m. Find: (a) the average retardation; (b) the average braking force in newtons. CA” J-ed The retardation is found from the formula, the valve ofa cylinder containing 12 kg of compressed gas is opened and the cylinder empties […]
Jet engines An aircraft jet engine works on the same principle as a rocket, the difference between them is concerned only with the method of obtaining the high-velocity gas jet. Fig. 4.10 shows, in simplified form, the construction of an axial-flow gas turbine or jet engine. The fuel used in these engines is kerosene (paraffin). This is sprayed […]
Rocket propulsion Now think of a toy rubber balloon which has been blown up with air and its secured with string. If the string is now removed so that the air can escape y. the balloon will, if released, dart round the room until all the air has gone. It e as a simple rocket. e rockets which […]
Newton’s third law of motion Whenever a force acts on one body, an equal and opposite force acts on some other body/This is sometimes stated, to every action there is an equal and opposite reaction. It is Important to realize that the action and reaction act on different bodies. This law has already been mentioned with reference […]
Weight of a body in a lift There must be few people who have not, at some time or other, travelled in a lift or elevator. So probably everyone is acquainted with the feeling of extra personal weight when the lift accelerates from rest to attain its steady upward velocity, together with a feeling of lightness when […]
Use of a calibrated spring balance The spring of the previous experiment may be used in conjunction with its Cali bra graph for the purpose of measuring unknown weights in newtons. Suppose, for example, the extension of the spring is 5 em when a piece of metal is placed in the From the graph (Fig. 4.5) it will […]
To calibrate a spring balance in newtons Forces or weights are often measured by means of a spring balance. The principle underlying the spring balance was first investigated in the seventeenth century by Robert Hooke. He showed that when a spring is fixed at one end and a force is applied to the other, the extension of the […]
Weight of a body expressed in newtons Galileo showed that all bodies, whatever their masses, have the same acceleration when they fall freely under the action of gravity. In equations, the acceleration due to gravity is denoted by the italic letter “g” to distinguish it from the Roman letter “g” used as the symbol for mass in […]
To verify experimentally that F x ma We may test the truth of Newton’s second law by measuring the accelerations produced when various forces are applied to ci-~~ecial trolley running on three ballbearing wheels (Fig. 4.2). The equation, F = ma, applies to any consistent system of units so we can save time in weighing and calculation if […]
Newton’s second law of motion T he rate of change of momentum of a body is proportional to the applied force and takes place in the direction in which the force acts. We shall now show how Newton’s second law of motion enables us to define an absolute unit of force which remains constant under all conditions. It […]