Science - Forces Flashcards
1
Q
What are forces?
A
- A force can be a push or a pull.
- For example, when you push open a door you have to apply a force to the door. You also have to apply a force to pull open a drawer.
- You cannot see a force but often you can see what it does.
2
Q
What can forces do?
A
- Change speed, direction or shape of an object.
- For example, when you pull on an elescatic band it changes shape.
3
Q
Measuring forces
A
- Forces are measured in Newtons using a forces meter (Newton Meter)
- The unit of force is called ‘N’
4
Q
What is MASS?
A
- The mass of an object is the amount of matter or “stuff” it contains.
- The more matter an object contains, the greater its mass. e.g An elephant contains more matter than a mouse, so it has a greater mass.
- Mass is measured in kilograms, kg, or grams, g.
5
Q
What is Gravity?
A
- The force that attracts objects towards each other.
6
Q
When does gravity increase?
A
- When the mass of an object increases AND when objects are closer together.
7
Q
What is weight?
A
- It is a FORCE caused by gravity.
- The weight of an object is the gravitational force between the object and the Earth.
- The more mass the object has the greater its weight will be.
8
Q
Why do you weigh less on the Moon than on Earth?
A
- The Moon has less mass than the Earth, so its gravity is less than the Earth’s gravity.
- This means that objects weigh less on the Moon than they do on the Earth.
9
Q
What is the Moon’s gravity compared to Earth?
A
- The Moon’s gravity is one sixth of the Earth’s gravity. A 120 kg astronaut weighs 1200 N on Earth.
- On the Moon they would weigh only 200 N.
- The astronaut’s mass is 120kg wherever they are.
10
Q
How do we work out ‘pressure’?
A
- Weight or Force applaied and area over which the force works.
11
Q
How do we measure pressure?
A
- Pressure = FORCE (divided by) AREA
- e.g A force of 20 N acted over an area of 2 m2 (two square metres) = 20 ÷ 2 = 10 N/m2
12
Q
Force diagrams
A
- We can show the forces acting on an object using a force diagram.
- Each force is shown as a force arrow.
- An arrow shows: the size of the force (the longer the arrow, the bigger the force) the direction in which the force acts.
13
Q
What do we mean by ‘balanced forces’?
A
- When two forces acting on an object are equal in size but act in opposite directions, we say that they are balanced forces.
14
Q
What happens if the forces on an object are balanced?
A
- An object that is not moving stays still.
- An object that is moving continues to move at the same speed and in the same direction.
15
Q
What is an unbalanced force?
A
- When two forces acting on an object are not equal in size, we say that they are unbalanced forces.
