A force is any pull or push that can put an object into motion, stop an object or change the way that it moves. A force can also deform or break an object.
2. What are the main types of forces? Give examples.
The main types of forces are contact forces and non-contact forces.
Contact forces act on objects by making physical contact, for example, a tennis player shots the ball with his tennis racket.
Non-contact forces act on objects without making physical contact, for example, a magnet attracting iron from a distance.
3. What type of force is magnetism?
The force of magnetism is a non-contact force.
4. What is the force of gravity? What does it depend on?
The force of gravity is a non-contact force that depends on an object’s mass and its distance from the Earth.
5. How do mass and distance affect the force of gravity?
Gravity is stronger on objects that have got more mass and on objects that are near the Earth.
6. Why do astronauts float in space?
Astronauts float on space because gravity is weaker on objects that are far from the Earth.
7. What is a machine?
A machine is a tool that multiplies force to make work faster and easier.
8. What is a simple machine?
A simple machine is a machine that usually has got one or two parts.
9. What is a complex machine?
Complex machines are combinations of two or more simple machines. They have got many parts.
10. In what everyday machines can we find gears?
We can find gears in clocks, bicycles and door handles.
11. What are the main types of simple machines?
The main types of simple machines are: the wheel, the pulley, the ramp, the lever and the screw.
12. How can we use a pulley?
We use pulleys to lift loads. When we pull down on one end of the rope the other end pulls up the load. We use the same amount of force, but the pulley makes the work more comfortable.
13. How can we use a ramp?
We use a ramp to go up and down. We can also use a ramp to move heavy loads more easily.
14. How can we use a lever?
We use levers to move and lift objects more easily.
15. How do we call the fixed point of a lever?
We call it fulcrum.
16. Let’s see how much you know about your bicycle: What is the part that connects the crank to the back wheel? What do you use to change the direction of the front wheel? What is the special wheel with metal gears? What does a cable to control the brake pull?
The part that connects the crank to the back wheel is the chain.
The part that we use to change the direction of the front wheel is the handlebar.
The special wheel with metal gears is the crank.
The cable to control the brake pulls the brake lever.
17. What is technology? What does it include?
Technology is the art of applying scientific knowledge to solve practical problems. It includes designing and building the necessary equipment.
18. What is the most important invention in the history of transport?
The most important invention in the history of transport is the wheel.
19. What type of engine have most aeroplanes got today?
Most aeroplanes use the jet turbine.
20. What did the steam engine give us?
The steam machine gave us a new way to power machines and vehicles.
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