1. Dynamics and Space Learning Intention You will be able to:
State the relationship between weight, mass and gravitational field strength.
Carry out calculations involving mass, weight and gravitational field strength within our solar system.

2. Weight, mass and gravitational field strength
Mass is the quantity of matter present in a body – the total of all the protons, neutrons and electrons it is made from. Mass is measured in kilograms (kg).
Weight is a force which is caused by the pull of gravity. On Earth, the weight of 1 kilogram is approximately 10 newtons.
We say g = 10 N/Kg where “g” is called “the gravitational field strength”.
Gravitational field strength is defined as “the weight per unit mass”.
Using a Newton balance measures weight.

3. To find the weight of any mass use the following:
W = mg
where: W is the weight measured in N
m is the mass measured in kg
g is the gravitational field strength (10 N/Kg on Earth).
eg what is the weight of a 55 kg pupil?
W = m g W =
W = 55 x 10 m = 55 kg
W – 550 N g = 10 N/kg

4. 1 Copy and complete this table:
object
mass (kg)
weight (N)
bag of sugar 1
bag of tatties
2.5
yourself
a car
1000

5. 2 A pupil carries a school bag, mass 5 kg, containing four books, each of mass 1 kg. What is the total weight of the schoolbag and its contents?

6. 3 What is the weight of a small apple – mass 0.1 kg?

7. The weight of a certain pupil is 640 N.
What is the pupil’s mass?

8. A car has a weight of N.
What is the mass of the car?

9. GRAVITATIONAL FIELD STRENGTH  
The gravitational field is the space around the Earth in which a mass experiences a force. At the surface that force is 10 N/kg. The force gets less as you move away from the surface because the value of the gravitational field strength gets smaller.
If you were able to travel to the other planets in the solar system you would find that although your mass stayed the same everywhere you went, your weight would change because “g” has different values on the other planets.
moon walking

10. 1 Look up your mass from the previous activity and enter it in the column head m.
(NB – your mass will be the same wherever you go).
Using the equation W = mg, calculate your weight on each of the planets shown in the table. Complete the column headed mg.
Planet
g (N/kg)
m (kg)
mg (N)
Mercury
3.7
Venus
8.9
Earth 10
(Moon)
1.6
Mars
Jupiter 23
Saturn
9.0
Uranus
8.7
Neptune 11
Pluto
0.81

11. Use your answers to the previous question to answer the questions below.
2a Name the planet in our solar system on which you would have the greatest weight.
2b Name the planet on which you would have a weight closest to your Earth weight.
2c Name the planet on which you would have the smallest weight.

12. 3 Watch the clip which falls faster and read the information in the planet table.
On what planet would the containers have the greatest acceleration? Explain your answer.

13. 2001 SQA General Q13.
A student carries out an experiment to measure the weight of a block.
The block is marked as having a mass of 1 kilogram as shown.
Copy and complete the following passage.
“Weight is a and is the Earth's pull on an object.
The weight of a mass of 1 kilogram is ”
(b) In doing the experiment, the student has the choice of the Newton balances shown below to measure the weight of the block.
Which balance could not be used
to measure the weight of the block?
Give a reason for your choice.

14. 2005 SQA General Q20 modified.
The table below gives some information about planets and other objects in our Solar System.
(a) On which two planets would a 5 kilogram mass have the same weight?