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Physics (Triple Award): All Topics
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What is the SI unit of mass, and its symbol?
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Edexcel IGCSE Physics (Triple Award)
Physics (Triple Award): All TopicsComplete deck
01·1(a) Units
What is the SI unit of mass, and its symbol?
Answer
The kilogram (kg). Mass is the amount of matter in an object and is always measured in kg in calculations.
02·1(a) Units
What is the SI unit of length (distance), and its symbol?
Answer
The metre (m). Distances moved, heights and lengths are all measured in metres in calculations.
03·1(a) Units
What is the SI unit of time, and its symbol?
Answer
The second (s). Times given in minutes, hours or days must be converted to seconds for calculations.
04·1(a) Units
What is the unit of speed and of velocity?
Answer
Metre per second (m/s). Speed = distance (m) ÷ time (s), so the unit is m ÷ s = m/s. Velocity has the same unit because it is speed in a given direction.
05·1(a) Units
What is the unit of acceleration, and how is it read aloud?
Answer
Metre per second squared (m/s²), read as 'metres per second squared' (or 'metres per second per second').
06·1(a) Units
What is the unit of force, and who is it named after?
Answer
The newton (N), named after Sir Isaac Newton. All forces, including weight, friction and thrust, are measured in newtons.
07·1(a) Units
What is the unit of gravitational field strength (g)?
Answer
Newton per kilogram (N/kg) – the number of newtons of gravitational force acting on each kilogram of mass.
08·1(a) Units
Which of the units kg, m and s are base units, and how are units such as m/s and m/s² obtained?
Answer
kg (mass), m (length) and s (time) are the base units used here. Other units are derived by combining them, e.g. m ÷ s = m/s for speed and (m/s) ÷ s = m/s² for acceleration.
09·1(a) Units
Is mass or weight measured in kilograms?
Answer
Mass is measured in kilograms (kg). Weight is a force (the pull of gravity on a mass), so it is measured in newtons (N).
10·1(a) Units
What is the approximate value of g on Earth, and what value is often used in calculations?
Answer
About 9.8 N/kg near the Earth's surface; 10 N/kg is often used to make calculations easier.
11·1(a) Units
What is the gravitational field strength on the Moon?
Answer
About 1.6 N/kg – so an object has less weight on the Moon even though its mass (in kg) is unchanged.
12·1(a) Units
In a physics answer, what does the unit symbol 'm' stand for?
Answer
Metre. Physics uses metric units, so 'm' is never miles (and m/s means metres per second, not miles per second).
13·1(a) Units
Roughly how big is a force of 1 N?
Answer
About the weight of an average-sized apple (~100 g). A 1 kg bag of sugar weighs about 10 N.
14·1(a) Units
What does the word 'per' (or the '/' sign) mean in a unit such as m/s or N/kg?
Answer
'Divided by' – e.g. m/s is metres divided by seconds (metres travelled each second); N/kg is newtons divided by kilograms (newtons on each kilogram).
15·1(a) Units
Name two quantities in Topic 1 that are both measured in m/s.
Answer
Speed and velocity. Velocity is a vector (speed in a stated direction); speed is a scalar.
16·1(a) Units
Why is the symbol for the newton a capital N, while the symbols for metre and second are lower-case?
Answer
Units named after a person (Newton) have a capital-letter symbol; others, such as m, s and kg, are written in lower case. The case matters – a lower-case letter in front of a unit can mean a prefix (e.g. mm = millimetre).
17·1(a) Units
Define one newton in terms of mass and acceleration.
Answer
One newton is the force needed to make a mass of 1 kg accelerate at 1 m/s² (from F = m × a).
18·1(a) Units
Explain why acceleration is measured in m/s².
Answer
Acceleration = change in velocity ÷ time taken. Change in velocity is in m/s and time is in s, so the unit is (m/s) ÷ s = m/s/s, written m/s².
19·1(a) Units
Convert 2.5 km into metres.
Answer
1 km = 1000 m, so 2.5 km = 2.5 × 1000 = 2500 m.
20·1(a) Units
Convert 45 cm into metres.
Answer
1 m = 100 cm, so 45 cm = 45 ÷ 100 = 0.45 m.
21·1(a) Units
Convert 350 mm into metres.
Answer
1 m = 1000 mm, so 350 mm = 350 ÷ 1000 = 0.35 m.
22·1(a) Units
Convert 0.75 m into millimetres.
Answer
1 m = 1000 mm, so 0.75 m = 0.75 × 1000 = 750 mm.
23·1(a) Units
Convert 500 g into kilograms.
Answer
1 kg = 1000 g, so 500 g = 500 ÷ 1000 = 0.5 kg.
24·1(a) Units
Convert 3 tonnes into kilograms.
Answer
1 tonne = 1000 kg, so 3 tonnes = 3 × 1000 = 3000 kg.
25·1(a) Units
Convert 2.5 minutes into seconds.
Answer
1 min = 60 s, so 2.5 min = 2.5 × 60 = 150 s.
26·1(a) Units
Convert 1.5 hours into seconds.
Answer
1 h = 60 × 60 = 3600 s, so 1.5 h = 1.5 × 3600 = 5400 s.
27·1(a) Units
How many seconds are there in one day?
Answer
24 h × 60 min × 60 s = 86 400 s.
28·1(a) Units
Convert 3.5 kN into newtons.
Answer
1 kN = 1000 N, so 3.5 kN = 3.5 × 1000 = 3500 N.
29·1(a) Units
How many newtons are there in 1 MN?
Answer
1 MN (meganewton) = 1 000 000 N = 10⁶ N.
30·1(a) Units
Convert 72 km/h into m/s.
Answer
Divide by 3.6: 72 ÷ 3.6 = 20 m/s. (Working: 72 km/h = 72 000 m ÷ 3600 s = 20 m/s.)