Mass and weight

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Apuntes de la lección

Mass and Weight – Key Definitions

Mass is the amount of matter in an object, measured in kilograms (kg).
Weight is a downwards force due to gravity, measured in newtons (N).
Mass stays the same everywhere; weight changes with gravitational field strength.
Gravitational field strength (g) is the force per unit mass, measured in N/kg.
On Earth, g = 9.8 N/kg; on the Moon, g = 1.6 N/kg.

The Weight Equation

Weight = Mass × Gravitational field strength (W = m × g).
To calculate weight: multiply mass (kg) by g (N/kg).
To calculate mass: rearrange to m = W ÷ g.
To calculate g: rearrange to g = W ÷ m.
Always include units in your answer (N for weight, kg for mass).

Worked Example – Calculating Weight

Example: A 20 kg object on the Moon (g = 1.6 N/kg).
Write equation: Weight = Mass × g.
Substitute: 20 kg × 1.6 N/kg = 32 N.
The weight is 32 N.

Worked Example – Calculating Mass

Example: An object weighs 0.74 N on Mars (g = 3.7 N/kg).
Rearrange: Mass = Weight ÷ g.
Substitute: 0.74 N ÷ 3.7 N/kg = 0.2 kg.
The mass is 0.2 kg.

Key Points to Remember

Weight is a force; it always acts downwards.
Gravitational field strength depends on the mass of the planet.
Even you attract other objects, but your mass is too small for a noticeable force.
On Earth, a 1 kg mass has a weight of 9.8 N.

Particle arrangement in solids, liquids and gases – mass is the amount of matter, weight depends on gravity.

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Preguntas de práctica

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1.What is the equation linking weight (W), mass (m), and gravitational field strength (g)?
Easy
- AW = m × g
- BW = m ÷ g
- CW = g ÷ m
- DW = m + g
2.Which of the following statements is true?
Easy
- AThe mass of an object is the same everywhere.
- BThe weight of an object is the same everywhere.
- CMass changes with location, but weight does not.
- DWeight is measured in kilograms.
3.What is the weight of a 0.5 kg book on Earth where g = 9.8 N/kg?
Easy
- A4.9 N
- B0.5 N
- C9.8 N
- D5.0 N
4.A Lunar Rover has a mass of 210 kg. What is its weight on the Moon where g = 1.6 N/kg?
Easy
- A336 N
- B131 N
- C210 N
- D1.6 N
5.A 2 kg rock on Venus has a weight of 17.6 N. What is the gravitational field strength on Venus?
Medium
- A8.8 N/kg
- B35.2 N/kg
- C0.11 N/kg
- D2.0 N/kg
6.On Pluto, g = 0.5 N/kg. What is the weight of a 4 kg object?
Easy
- A2.0 N
- B0.5 N
- C8.0 N
- D4.5 N
7.An object on Ceres has weight 0.81 N and mass 3 kg. What is g on Ceres?
Medium
- A0.27 N/kg
- B2.43 N/kg
- C3.7 N/kg
- D0.81 N/kg
8.Dr Edmunds has mass 70 kg and weight 259 N on Mercury. What is g on Mercury?
Medium
- A3.7 N/kg
- B0.27 N/kg
- C9.8 N/kg
- D259 N/kg

Más preguntas

9.At the top of Mount Everest, g = 9.77 N/kg. A water bottle weighs 12 N. What is its mass?
Medium
- A1.23 kg
- B0.81 kg
- C12 kg
- D9.77 kg
10.A can of cola has mass 330 g (0.33 kg) and weight 2.3 N. What is the gravitational field strength?
Medium
- A6.97 N/kg
- B0.14 N/kg
- C2.3 N/kg
- D330 N/kg
11.Which of the following is the correct unit for weight?
Easy
- Anewton (N)
- Bkilogram (kg)
- CN/kg
- Dkg N
12.What does the mass of an object depend on?
Easy
- AThe amount of matter in the object
- BThe gravitational field strength
- CThe weight of the object
- DThe location of the object
13.An astronaut has a mass of 80 kg on Earth. When she travels to the Moon, where gravitational field strength is 1.6 N/kg, what is her weight on the Moon?
Medium
- A128 N
- B784 N
- C80 N
- D50 N
14.A bag of sugar weighs 49 N on Earth (g = 9.8 N/kg). What is its mass?
Easy
- A5 kg
- B0.2 kg
- C480.2 kg
- D49 kg
15.On planet X, a 10 kg mass has a weight of 150 N. What is the gravitational field strength on planet X?
Easy
- A15 N/kg
- B0.067 N/kg
- C1500 N/kg
- D10 N/kg
16.A student measures the weight of a 1 kg mass on Earth using a spring balance. What reading should she expect? (g = 9.8 N/kg)
Easy
- A9.8 N
- B1 N
- C0.102 N
- D9.8 kg
17.The weight of an object on Earth is 100 N. What would its weight be on a planet where gravitational field strength is half that of Earth? (g_Earth = 9.8 N/kg)
Medium
- A50 N
- B100 N
- C200 N
- D25 N
18.A spaceship has a mass of 5000 kg. On Earth, its weight is 49000 N. If it lands on Mars where g = 3.7 N/kg, what is its weight on Mars?
Medium
- A18500 N
- B5000 N
- C49000 N
- D13514 N
19.A student plots a graph of weight (y-axis) against mass (x-axis) for objects on Earth. What is the gradient of the line?
Medium
- A9.8 N/kg
- B1 kg/N
- C9.8 m/s²
- D0.102 kg/N
20.A 2 kg rock is taken from Earth to the Moon. Which statement about its mass and weight is correct?
Medium
- AMass stays the same, weight decreases.
- BMass decreases, weight stays the same.
- CBoth mass and weight decrease.
- DBoth mass and weight stay the same.
21.Which of the following is the unit of gravitational field strength?
Easy
- AN/kg
- Bkg/N
- CN
- Dkg
22.A spring balance calibrated on Earth (g = 9.8 N/kg) is used on Mars (g = 3.7 N/kg) to weigh a 1 kg mass. What reading does it show?
Medium
- A3.7 N
- B9.8 N
- C1 N
- D2.65 N
23.An object has a mass of 0.5 kg. What is its weight on Earth? (g = 9.8 N/kg)
Easy
- A4.9 N
- B0.5 N
- C9.8 N
- D5.0 N
24.A Lunar Rover has a mass of 210 kg. Calculate its weight on the Moon where g = 1.6 N/kg.
Easy
- A336 N
- B210 N
- C131.25 N
- D2058 N
25.A student uses a spring balance to measure the weight of a 1 kg mass on Earth (g = 9.8 N/kg). She then takes the same spring balance and the same mass to the Moon (g = 1.6 N/kg). Which statement about the readings is correct?
Medium
- AThe spring balance shows 9.8 N on Earth and 1.6 N on the Moon.
- BThe spring balance shows 1.6 N on Earth and 9.8 N on the Moon.
- CThe spring balance shows 9.8 N on both Earth and the Moon.
- DThe spring balance shows 1.6 N on both Earth and the Moon.
26.A student measures the weight of an object on Earth as 50 N. She then takes the object to a planet where the gravitational field strength is one-fifth of Earth's. What is the mass of the object on that planet? (g_Earth = 9.8 N/kg)
Medium
- A5.1 kg
- B50 kg
- C10.2 kg
- D2.0 kg
27.Which of the following is the correct unit for gravitational field strength?
Easy
- AN/kg
- Bkg/N
- CN
- Dkg
28.A student calibrates a spring balance on Earth (g = 9.8 N/kg) so that it reads weight directly. She then uses it on Mars (g = 3.7 N/kg) to weigh a 1 kg mass. What reading does it show?
Medium
- A3.7 N
- B9.8 N
- C1.0 N
- D0.38 N
29.A student measures the weight of a 1 kg mass on Earth using a spring balance. He then uses the same spring balance to measure the weight of the same mass on the Moon. The spring balance gives a different reading. Which of the following is the best explanation?
Medium
- AThe spring balance measures weight, and weight changes with gravitational field strength.
- BThe spring balance measures mass, and mass changes with gravitational field strength.
- CThe spring balance is faulty because it should give the same reading everywhere.
- DThe spring balance measures weight, but weight is constant everywhere.
30.Which of the following is the correct definition of mass?
Easy
- AThe amount of matter in an object
- BThe force of gravity on an object
- CThe weight of an object
- DThe volume of an object
31.Which of the following is the correct definition of weight?
Easy
- AThe amount of matter in an object
- BThe force of gravity on an object
- CThe mass of an object
- DThe volume of an object
32.Which of the following statements about mass is true?
Easy
- AMass is measured in newtons
- BMass is the same everywhere
- CMass is a force
- DMass changes with location
33.Which of the following statements about weight is true?
Easy
- AWeight is measured in kilograms
- BWeight is the same everywhere
- CWeight is a force due to gravity
- DWeight is the amount of matter
34.What is the weight of a 0.5 kg book on Earth? (g = 9.8 N/kg)
Easy
- A4.9 N
- B0.5 N
- C9.8 N
- D5.0 N
35.A student measures the weight of a 1 kg mass on Earth using a spring balance. She then takes the same spring balance and the same mass to the Moon (g = 1.6 N/kg). What weight will the spring balance read on the Moon?
Medium
- A1.6 N
- B9.8 N
- C0.16 N
- D6.1 N
36.An object has a weight of 50 N on Earth (g = 9.8 N/kg). What is its mass?
Easy
- A5.1 kg
- B490 kg
- C0.196 kg
- D50 kg
37.On Earth, a spring balance calibrated in newtons shows a reading of 10 N for a certain object. The same object is taken to a planet where the gravitational field strength is 4.0 N/kg. What will the spring balance read? (g on Earth = 9.8 N/kg)
Medium
- A4.08 N
- B10 N
- C24.5 N
- D2.45 N
38.A student plots a graph of weight (y-axis) against mass (x-axis) for objects on Earth. What does the gradient of the line represent?
Medium
- Agravitational field strength
- Bmass
- Cweight
- Ddensity
39.A student uses a spring balance to measure the weight of a 1 kg mass on Earth (g = 9.8 N/kg). She then takes the same spring balance and the same mass to the Moon (g = 1.6 N/kg). What will the spring balance read on the Moon?
Medium
- A1.6 N
- B9.8 N
- C0.16 N
- D6.1 N
40.An object on Earth has a weight of 100 N. What would its weight be on a planet where the gravitational field strength is half that of Earth? (g_Earth = 9.8 N/kg)
Medium
- A50 N
- B100 N
- C200 N
- D25 N
41.Weight is a downwards force due to gravity.
Easy
True or false?
42.The mass of an object is the same everywhere.
Easy
True or false?
43.The weight of an object is the same everywhere.
Easy
True or false?
44.What is the gravitational field strength on the surface of Earth?
Easy
- A9.8 N/kg
- B1.6 N/kg
- C0.5 N/kg
- D8.8 N/kg
45.An astronaut has a mass of 80 kg on Earth. When she travels to the Moon (g = 1.6 N/kg), what is her weight on the Moon?
Medium
- A128 N
- B80 N
- C784 N
- D50 N
46.Match each quantity with its correct unit.
Easy
- Mass
- Weight
- Gravitational field strength
- kg
- N
- N/kg
47.Arrange the following steps in the correct order to calculate the weight of a 20 kg mass on the Moon (g = 1.6 N/kg).
Easy
- Write down equation: Weight = Mass × Gravitational field strength
- Calculate answer: 32 N
- Insert values: = 20 kg × 1.6 N/kg
48.Which of the following statements about mass and weight are true? (Select all that apply)
Medium
- AMass is the amount of matter in an object.
- BWeight is a force measured in newtons.
- CMass can change depending on location.
- DWeight is the same everywhere in the universe.
- EWeight depends on gravitational field strength.
49.The weight of an object is the same everywhere in the universe.
Easy
True or false?
50.A student measures the weight of a 1 kg mass on Earth using a spring balance calibrated in newtons. She then takes the same spring balance and the same mass to the Moon where g = 1.6 N/kg. What will the spring balance read on the Moon?
Medium
- A1.6 N
- B9.8 N
- C6.1 N
- D0.16 N
51.A rock of mass 2 kg is on the surface of Venus. The gravitational field strength on Venus is 8.8 N/kg. Calculate the weight of the rock.
Medium
52.An object on the surface of Ceres has a weight of 0.81 N and a mass of 3 kg. Calculate the gravitational field strength on Ceres.
Medium
53.Complete the sentence using the words provided: (mass, weight, gravitational field strength)
Easy
The amount of matter in an object is its ____. The force of gravity on an object is its ____. The strength of gravity at a location is called ____.
54.State the equation that links weight, mass and gravitational field strength.
Easy
55.A rock of mass 2 kg is on the surface of Venus. The gravitational field strength on Venus is 8.8 N/kg. Calculate the weight of the rock.
Medium
- A16.6 N
- B18.6 N
- C19.6 N
- D17.6 N
56.An object on the surface of Ceres has a weight of 0.81 N and a mass of 3 kg. Calculate the gravitational field strength on Ceres.
Medium
- A-0.73 N/kg
- B2.27 N/kg
- C0.27 N/kg
- D1.27 N/kg

Apuntes de repaso

## Mass and Weight - **Mass** is the amount of matter in an object, measured in kilograms (kg). It stays the same everywhere. - **Weight** is a downwards force due to gravity, measured in newtons (N). It changes with gravitational field strength. - **Gravitational field strength (g)** on Earth is 9.8 N/kg. ### Key Equation **Weight = Mass × Gravitational field strength** ### Rearranging - Mass = Weight ÷ Gravitational field strength - Gravitational field strength = Weight ÷ Mass ### Examples - On Moon (g = 1.6 N/kg): weight of 20 kg mass = 20 × 1.6 = 32 N - On Mars (g = 3.7 N/kg): mass of object with weight 0.74 N = 0.74 ÷ 3.7 = 0.2 kg ### Important Points - Weight is a force, always downwards. - Mass is constant; weight varies with gravity. - Use correct units: kg for mass, N/kg for g, N for weight.

Mass: The amount of matter in an object, measured in kilograms (kg). It stays the same wherever it is.
Weight: A downwards force due to gravity, measured in newtons (N). It can change depending on gravitational field strength.
Gravitational field strength (g): The force of gravity per unit mass, measured in N/kg. On Earth it is 9.8 N/kg.
Weight = Mass × Gravitational field strength: The equation used to calculate weight from mass and gravitational field strength.

Tarjetas

What is weight?

Weight is a downwards force due to gravity.

What is the equation linking weight, mass, and gravitational field strength?

Weight = Mass × Gravitational field strength.

What is mass?

Mass is the amount of matter an object contains, measured in kilograms (kg).

Does mass change with location?

No, mass stays the same wherever it is.

Does weight change with location?

Yes, weight can change depending on the gravitational field strength.

What is the gravitational field strength on Earth's surface?

9.8 N/kg.

What is the gravitational field strength on the Moon?

1.6 N/kg.

Calculate the weight of a 20 kg mass on the Moon (g=1.6 N/kg).

Weight = 20 kg × 1.6 N/kg = 32 N.

Calculate the weight of a 0.5 kg book on Earth (g=9.8 N/kg).

Weight = 0.5 kg × 9.8 N/kg = 4.9 N.

Calculate the weight of a 210 kg Lunar Rover on the Moon (g=1.6 N/kg).

Weight = 210 kg × 1.6 N/kg = 336 N.

Calculate the weight of a 2 kg rock on Venus (g=8.8 N/kg).

Weight = 2 kg × 8.8 N/kg = 17.6 N.

Calculate the weight of a 4 kg object on Pluto (g=0.5 N/kg).

Weight = 4 kg × 0.5 N/kg = 2 N.

An object has weight 0.81 N and mass 3 kg on Ceres. Find g.

g = Weight ÷ Mass = 0.81 N ÷ 3 kg = 0.27 N/kg.

Dr Edmunds has mass 70 kg and weight 259 N on Mercury. Find g.

g = Weight ÷ Mass = 259 N ÷ 70 kg = 3.7 N/kg.

A water bottle has weight 12 N at the top of Everest (g=9.77 N/kg). Find its mass.

Mass = Weight ÷ g = 12 N ÷ 9.77 N/kg ≈ 1.23 kg.

A can of cola has mass 330 g and weight 2.3 N. Find g.

Mass = 0.33 kg; g = Weight ÷ Mass = 2.3 N ÷ 0.33 kg ≈ 6.97 N/kg.

What is gravitational field strength?

It is the force per unit mass due to gravity at a point, measured in N/kg.

What determines the gravitational field strength at a planet's surface?

The planet's mass determines its gravitational field strength.

True or false: Weight is the same everywhere.

False. Weight changes with gravitational field strength.

True or false: Mass is the same everywhere.

True. Mass is constant regardless of location.

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