Name some forces.
-gravity or weight always acting straight down
-reaction force from a surface, usually acting straight upwards
-thrust or push or pull due to an engine or rocket speeding something up
drag or air resistance or friction which s slowing the thing down
-lift due to aeroplane wings’
-tension in a rope or cable
What is a reaction force?
- the force that works against another to balance it
- e.g.gravity is acting downwards, causing a reaction force from the surface to push up on the object
When do you get acceleration?
- with an overall resultant unbalanced force
- the bigger the unbalanced force the greater the acceleration
How does friction occur?
- frictionbetween solid surfaces gripping
- friction between solid surfaces which are sliding over each other
- resistance or drag from fluids (liquids or gases)
How does friction work?
- when an object is moving friction acts in a direction that opposes friction
- to match the size of the force trying to move it, up until a point where afterwards the friction will be less than the other force and the object will move
How can you reduce drag?
- reduce surface area
- and have a streamline shape
How does friction work in a fluid?
-friction(drag) always increases as speed increases
What is terminal speed and how is it reached?
-when the forces have been balanced and a maximum speed has been reached
What does the terminal speed of an object depend on?
- on drag
- the greater the drag the lower the terminal speed will be
What does a balanced force do?
-keep an object moving at the same speed in the same direction (if it starts off still, it stays still)
What does an unbalanced force do?
-causes an object to accelerate in the direction of the force
What is resultant force?
- the final force
- all the forces working on an object added together
- single force that has the same effect on the object as all the individual forces acting together.
What is the size of acceleration determined by?
-force/mass
