Machines: the basics
A FORCE is a push or a pull that can cause and object to move or change direction. We measure force in NEWTONS (N), which tells us how much effort is being applied in a specific direction.
One example of a force is GRAVITY, which pulls us towards Earth. Gravity is a force that attracts all objects with MASS (i.e.everything!). Our mass is simply how much matter (stuff) we are made of and can be measured in KILOGRAMS (kg). This never changes, unless you add bits on or take them off.
Gravity gives us WEIGHT, which is measured in N or kg. On Earth, our mass and our weight are the same. However, if we go somewhere where gravity is different, our mass stays the same but our weight changes. The same things happens if you put an object in water - the mass doesn’t change, but the upwards force of the water makes the object seem lighter.
a. How many kilograms (kg) are equal to one Newton (N) on Earth?
100 grams are 1 Newton, so 1kg is 10 N.
To make an object move, we must apply a force. We call this EFFORT.
b. What unit do we use to measure effort?
Newtons, maybe?
Sometimes, the effort required to carry out a task is too much - but because we are human geniuses, we can use machines to help us.
c. In what three ways can machines change a force?
- Change the size of a force, e.g - car jack.
- Change the direction, e.g - curtain cord.
- Change the speed, e.g - eggbeater.
d. There are three main types of machines:
- Simple machines, which do one thing, such as levers, inclined planes, wheels or gears.
- Complex machines, which has 2 or more simple machines, like a bike.
- Engines, or powered machines, like cars.
