A 8000 kg engine pulls a train of 5 wagons, each of 2000 kg, along a horizontal track. If the engine exerts a force of 40000 N and the track offers a friction force of 5000 N, then calculate:
(a) the net accelerating force;
(b) the acceleration of the train; and
(c) the force of wagon 1 on wagon 2.
Mass of engine = 8000 kg
Mass of 1 wagon = 2000 kg
Mass of 5 wagons = 2000 x 5 = 10000 kg
Force exerted by the engine, F = 40000 N
Frictional force offered by the track, Ff = 5000 N
(a) Net force, Fa = Force of engine - Force of friction = F − Ff
= 40000 − 5000 = 35000 N
Hence, the net accelerating force is 35000 N.
(b) Total mass of the train, M = mass of 5 wagons + mass of engine
= 10000 + 8000 = 18000 kg
From Newton’s second law of motion:
Force = Mass x acceleration
35000 = 18000 x a
a = 35000 / 18000 = 1.94 m/s2
Hence, the acceleration of the train is 1.94 m/s2.
Convert into mole.
(a) 12 g of oxygen gas
(b) 20 g of water
(c) 22 g of carbon dioxide.
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You find your mass to be 42 kg on a weighing machine. Is your mass more or less than 42 kg?
What happens to the force between two objects, if
(i) the mass of one object is doubled?
(ii) the distance between the objects is doubled and tripled?
(iii) the masses of both objects are doubled?
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Illustrate the law of conservation of energy by discussing the energy changes which occur when we draw a pendulum bob to one side and allow it to oscillate. Why does the bob eventually come to rest? What happens to its energy eventually? Is it a violation of the law of conservation of energy?
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• if you get jaundice,
• if you get lice,
• if you get acne.
Why?
Name the technique to separate
(i) butter from curd,
(ii) salt from sea-water,
(iii) camphor from salt.
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A stone is released from the top of a tower of height 19.6 m. Calculate its final velocity.
What is the mass of:
(a) 0.2 mole of oxygen atoms?
(b) 0.5 mole of water molecules?
You find your mass to be 42 kg on a weighing machine. Is your mass more or less than 42 kg?
A bus decreases its speed from 80 km h-1 to 60 km h-1 in 5 s. Find the acceleration of the bus.
Write down the formulae of
(i) sodium oxide
(ii) aluminium chloride
(iii) sodium suphide
(iv) magnesium hydroxide
Why is it not possible to see an atom with naked eyes?
Name the technique to separate
(i) butter from curd,
(ii) salt from sea-water,
(iii) camphor from salt.
Convert into mole.
(a) 12 g of oxygen gas
(b) 20 g of water
(c) 22 g of carbon dioxide.
Explain the following giving examples.
(a) saturated solution
(b) pure substance
(c) colloid
(d) suspension
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Suppose you and your friend are on the moon. Will you be able to hear any sound produced by your friend?