A train is sounding its horn as it approaches a station. The engine driver hears a note of frequency f0 and of constant amplitude as the train slows down and…

Calcium nitride, Ca 3N2 , reacts with water to form calcium hydroxide and molecule X. No other products are formed, and molecule X contains only nitrogen and hydrogen atoms. What…

The family tree shows the inheritance of a recessive condition. Which of the following statements is/are correct?1 Individuals 1 and 2 are both heterozygous for this condition.2 Individuals 3 and…

A circle is drawn with centre (3, 5). A tangent is drawn to the circle. The tangent touches the circle at the point (6, 7). What is the gradient of…

A high-voltage dc overhead cable carries a current of 2000 A. One 20 m section of the cable has a mass of 120 kg. This cable section is supported so…

Three elements from Group 1 and three elements from Group 17 are given in the table with their relative atomic masses.Group 1 Group 17lithium (7) fluorine (19)sodium (23) chlorine (35.5)potassium…

A nucleotide consists of three different sub-units. A section of double-stranded DNA consists of 600 of these sub-units in total. Of these sub-units, 28 are the base adenine. What percentage…

The area of triangle PQR is 42 cm 2 .The length of PR is 8 cm.cos ș = 3/4What is the length of QR, in cm? Answer:

An electric shower heater is rated at 8.4 kW and raises the temperature of flowing water from 16 °C to 36 °C. What is the mass of water passing through…

Dry air can be cooled and then fractionally distilled to separate its components. What is the minimum volume of dry air needed to prepare a 25 dm3 sample of oxygen…