5.3 Weight, mass and gravity
9 exam questions worth 25 marks. Write your answer, open the mark scheme, then give yourself the marks you earned. Your answers are saved on this device.
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What is the unit of weight?
Choose one answer.
Correct Not quite: the answer is Newton
Mark scheme
B: Newton
Model answer
Newton (B).
Calculate the weight of a 4.0 kg bag of sugar on the Earth. (g = 9.8 N/kg)
Mark scheme
W = m g = 4.0 × 9.8 (1); 39.2 N (1)
Model answer
W = m g = 4.0 × 9.8 = 39.2 N.
An astronaut has a mass of 75 kg. Calculate her weight on the Moon, where the gravitational field strength is 1.6 N/kg.
Mark scheme
W = m g = 75 × 1.6 (1); 120 N (1)
Model answer
W = m g = 75 × 1.6 = 120 N.
A newtonmeter shows that an object weighs 24.5 N on the Earth. Calculate its mass. (g = 9.8 N/kg)
Mark scheme
m = W ÷ g (1); 24.5 ÷ 9.8 (1); 2.5 kg (1)
Model answer
m = W / g = 24.5 / 9.8 = 2.5 kg.
A probe has a mass of 50 kg and a weight of 185 N on the surface of Mars. Calculate the gravitational field strength on Mars.
Mark scheme
g = W ÷ m (1); 185 ÷ 50 (1); 3.7 N/kg (1)
Model answer
g = W / m = 185 / 50 = 3.7 N/kg.
An astronaut travels from the Earth to the Moon. State what happens to (a) her mass and (b) her weight. Explain your answers.
Mark scheme
(a) mass stays the same (1); because mass is the amount of matter in her body (1); (b) weight decreases (1); because the gravitational field strength on the Moon is smaller (1)
Model answer
(a) Her mass stays the same, because it is the amount of matter in her body. (b) Her weight decreases, because the gravitational field strength on the Moon is smaller than on the Earth.
State the difference between mass and weight, including the unit of each.
Mark scheme
mass is the amount of matter (1); measured in kg (1); weight is the force of gravity on an object (1); measured in newtons (1)
Model answer
Mass is the amount of matter in an object and is measured in kilograms. Weight is the force due to gravity on an object and is measured in newtons.
Describe how you would use a newtonmeter and some known masses to show that weight is directly proportional to mass.
Mark scheme
hang different masses from the newtonmeter (1); record the mass and the weight in each case (1); plot weight against mass (1); a straight line through the origin shows direct proportionality (1)
Model answer
Hang a series of different known masses from the newtonmeter and record the weight for each one. Plot a graph of weight against mass. A straight line through the origin shows that weight is directly proportional to mass.
A metre ruler is hung from a nail through a hole at one end. Describe where its centre of mass is, relative to the nail, when it comes to rest.
Mark scheme
directly below the nail (1); at the middle of the ruler (50 cm mark) (1)
Model answer
The centre of mass is directly below the nail, in line with the middle (50 cm mark) of the ruler.
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