Two satellites orbiting the Earth are situated on opposite sides of the Earth. Satellite A has a mass of 3 800 kg and Satellite B has a mass of 4 500 kg. Satellite A is at a height of 25 000 km above the surface of the Earth. 5.1 State Newton’s Universal Gravitational Law in … Read more
Two blocks, of mass 8 kg and 4 kg respectively, are joined with an inelastic string of negligible mass. The string runs over a frictionless pulley. The 8 kg block is on a horizontal surface while the 4 kg block is on an inclined plane of 40° with the horizontal. The coefficient of kinetic friction … Read more
A hovering rescue helicopter has a container of supplies, with a weight of 1 960 N, hanging from a cable. The tension in the cable is 2 100 N. 3.1 State Newton’s First Law of Motion in words. (2) 3.2 Draw a labelled force-diagram of ALL the forces acting on the container. (3) 3.3 Why … Read more
The discovery of gold played a significant role in the economic development of SouthAfrica. In 1970 gold mining in South Africa contributed 68 per cent to global production. 10.1 Which TWO mining methods are used in South Africa? (2) 10.2 Give TWO reasons why mining is important for the South African economy. (2) 10.3 State … Read more
A silver Christmas tree can be made by placing copper wire, shaped in the form ofa tree, into a silver nitrate solution. The unbalanced equation for the reaction is: Cu(s) + AgNO3(aq) → Cu(NO3)2(aq) + Ag(s) 9.1 Define the term oxidation in terms of oxidation number. (2) 9.2 Write down the following for the reaction … Read more
8.1 Define an acid in terms of the Lowry-Brønsted theory. (2) 8.2 Consider the following acid-base reaction: H2PO4+ NH3 → HPO42- + NH4+ 8.2.1 Identify the conjugate acid-base pairs in the above reaction. (4) 8.2.2 Define the term ampholyte. (1) 8.2.3 Choose an ampholyte in the above reaction. (2) 8.3 Ten grams (10 g) of … Read more
Methane is used as an alternative fuel. The combustion of methane releases carbondioxide and water. The balanced equation for this reaction is:CH4(g) + O2 (g) → CO2 (g) + 2H2O (g) + 891 kJ.mol-1 The activation energy for this reaction is 172 kJ.mol-1. 7.1 Is this reaction ENDOTHERMIC or EXOTHERMIC? Give a reason for theanswer. … Read more