7K Forces and their effects Identifying forces Friction Weight Forces summary

7K Forces and their effects Identifying forces

a push a pull a turn What is a force and what does it do? A force is… 7K Identifying forces - What is a force? What is a force and what does it do? A force is… a push a pull a turn You cannot see a force. But you can feel a force and see the effect of the force. Forces make things happen or stop them from happening. Name 5 ways in which you have used a force today.

Forces can effect things in 3 ways. Can you name them? 7K Identifying forces – Effects of a force Forces can effect things in 3 ways. Can you name them? Effect 1. A force can change the shape of an object. Effect 2. A force can change the speed of an object, making it faster or slower. Effect 3. A force can change the direction of an object.

picture to find the force 7K Forces - Find the force In each picture, identify the main force and describe its effect. TEACHER’S NOTES For each force picture, clicking on the central box - reveals the image - reveals the force arrow or arrows - moves onto the next image Click on the picture to find the force

7K Forces Friction

friction Put your palms together and rub hard. What happens? 7K Friction – What is friction? Put your palms together and rub hard. What happens? friction You are creating the force called . Friction occurs when any two surfaces move against each other and tries to stop the movement. Heat is generated as a result of friction. Which type of surface generates more friction, a rough surface or a smooth surface?

7K Friction – Take the rough with the smooth

What forces are acting on a racing car travelling at a constant speed?  7K Friction – Thrust and drag forces What forces are acting on a racing car travelling at a constant speed? Drag forces oppose the thrust force and slow the car. Where are these frictional forces? drag A thrust force makes the car move forward. Where does this force come from? thrust The friction of air against the body of the car also opposes the car’s movement. This type of friction is called air resistance. The friction of the tyres on the road opposes movement of the car.

 7K Friction – Thrust and drag forces When the thrust and drag forces are balanced, the car travels at a constant speed. drag thrust What happens to the speed of the car when the thrust and drag forces are unbalanced?

7K Friction – High or low?

7K Forces and their effects Weight

Why doesn’t water come out of the tap sideways? 7K Weight – What is gravity? Why doesn’t water come out of the tap sideways? Why does rain always fall downwards towards the Earth? Why don’t people on the other side of the Earth fall off into outer space?

gravity The answer to all these questions is the force called… 7K Weight – What is gravity? The answer to all these questions is the force called… gravity

The pulling force of gravity always acts towards the 7K Weight – What is weight? The pulling force of gravity always acts towards the centre of the Earth, wherever you are on the planet.

7K Weight – What is weight? The effect of the force of gravity on an object is called the object’s… weight Weight is a force and is measured in Newtons. Why is weight different to mass?

The girl below is not moving. Are there any forces acting on her? 7K Weight - Balanced forces The girl below is not moving. Are there any forces acting on her? An upwards force is produced by the chair in the opposite direction to gravity. The girl’s weight due to the force of gravity is pulling her mass down on the chair. The girl does not move because these forces are balanced. What does this tell you about the size of these forces?

Gravity changes depending on where you are in the Universe. 7K Weight – Changes in weight Gravity changes depending on where you are in the Universe. What happens to weight and mass when gravity changes?   Our friendly alien Ms. R. Nerg will help you find out more…

On Earth, a mass of 1 kg has a weight of 10 N. My mass is 42 kg. 7K Weight – Changes in weight On Earth, a mass of 1 kg has a weight of 10 N. My mass is 42 kg. What is my weight on Earth?

The force of gravity on the Moon is 7K Weight – Changes in weight The force of gravity on the Moon is 6 times less than on Earth. My mass is still 42 kg. What is my weight on the Moon?

My weight in outer space is 0 N. 7K Weight – Changes in weight In outer space, far away from any planets or stars, there is no gravity pulling on me. My weight in outer space is 0 N. What is my mass in outer space?

7K Weight – Force of water Have you ever noticed how difficult it is to push an inflatable under water?   That’s because the water exerts an upwards force on the inflatable.   The upward force that acts on things in a liquid is called… upthrust How does upthrust help things float?

What forces are acting on the rubber duck as it floats? 7K Weight – Why do things float? What forces are acting on the rubber duck as it floats? Upthrust of water pushes upwards against the weight of the duck.   Weight of the duck due to the force of gravity pulls downwards.   The floating rubber duck is not moving.   What does this tell you about the forces acting on it?

7K Forces and their effects Forces summary

1. “Feel the force” is a well-known saying from which famous film? 7K Forces summary – “Feel the force!” 1. “Feel the force” is a well-known saying from which famous film? a) Star Wars. b) Star Trek. c) Stars in Your Eyes. 2. The units that forces are measured in are called… a) metres. b) newts. c) newtons. TEACHER’S NOTES Answers: 1a) 2c)

3. Gravity and magnetism are examples of… a) contact forces. 7K Forces summary – “Feel the force!” 3. Gravity and magnetism are examples of… a) contact forces. b) non-contact forces. c) police forces. 4. The force that occurs when two surfaces move against each other is called… a) Fred. b) fiction. c) friction. TEACHER’S NOTES Answers: 3b) 4c)

7K Forces summary – “Feel the force!” 5. In icy weather roads are covered with sand. How does the sand effect the amount of friction between car tyres and the road? a) Reduces friction. b) Increases friction. c) Has no effect. 6. A dog being taken for a walk is pulling on the lead held by its owner. The pulling force of the dog increases. What happens to the speed of its owner? a) Speeds up. b) Slows down. c) Changes direction. TEACHER’S NOTES Answers: 5b) 6a)

7K Forces summary – “Feel the force!” 7. The upwards force that slows down a sky diver as they fall through the air is called… a) weight. b) air conditioning. c) air resistance. 8. The pulling force of the Earth’s gravity always acts towards the centre of… a) the Moon. b) the Earth. c) the Sun. TEACHER’S NOTES Answers: 7c) 8b)

10. A computer on a desk does not move because there are… 7K Forces summary – “Feel the force!” 9. A cyclist is travelling at a constant speed. The balanced pair of forces acting on the cyclist are… a) thrust and weight. b) thrust and drag. c) thrust and upthrust. 10. A computer on a desk does not move because there are… a) no forces acting on it. b) unbalanced forces acting on it. c) balanced forces acting on it. TEACHER’S NOTES Answers: 9b) 10c)

7K Forces summary – “Feel the force!” 11. An astronaut drops a 1 kg bar of chocolate in outer space. What is the weight of the bar of chocolate? a) 10 N. b) 1 N. c) 0 N. 12. A spacecraft has a mass of 9000 kg on Earth. What would its weight be on the Moon? a) 1500 N. b) 9000 N. c) 54 000 N. TEACHER’S NOTES Answers: 11c) 12b)