Forces

Slide 1

• Physical quantities can be vectors or scalars.
• Scalar
• Has only magnitude. It means it can be described by number only, for example mass, charge, speed, time or distance.
• We can simply add scalars (think that when you have 2kg of apples and 4kg of oranges, you have 6kg of fruits).

Slide 2

• Vectors
• Have both magnitude and direction.
• We are concerned not only how big is the quantity, but also in which direction does it point.
• For example velocity describes how quickly an object moves (lets say the car goes 60km/h), but also in which direction (lets say this car goes left).
• THE ONLY VECTOR YOU NEED TO KNOW NOW IS FORCE.

Slide 3

• FORCE
• It is an interaction between two objects.
• It is measured in Newtons by a force meter.
• It has both direction and magnitude.
• (for example we can push a box standing on the floor by applying a force of 6N towards right)
• Adding forces is different than adding scalars, as they can act in opposite directions.
• (for example when another person will push the same box to the left with 4N towards left, the RESULTANT FORCE acting on the box will be 2N towards right)

Slide 4

• Force is needed to change the way the object moves.
• For example to make a ball lying on the floor move, you need to kick it. By kicking it you supply force to make it move.
• When the ball starts to move, its speed increases (it is 0m/s at the start). This process is called acceleration.
• Force can also change the direction of a moving object.
• For example when the ball is going towards your goal, you can kick it (apply force) to send it in an opposite direction.

Slide 5

• NEWTON'S FIRST LAW
• Says that when there is NO FORCE acting on an object or the FORCES TOWARDS LEFT AND RIGHT ARE THE SAME (so the resultant force is 0N)
• the object will be either RESTING or MOVE IN THE SAME WAY (which means that it won't accelerate or change direction).