Year 8 Forces Flashcards
What is friction?
The force between two surfaces in contact with each other as they move
What is upthrust?
The upwards force that a liquid or gas exerts on a body floating in it
What is lift?
The upward force that acts on an aircraft wing
What is reaction?
When an object rests on a surface, its weight is balanced by a force from the ground
What is Hooke’s Law?
That the extension of an elastic object is directly proportional to the force applied to it:
F = K x E
F is the force in Newtons
K is the spring constant in Newtons/ metre
E is the extension in metres
What is work done?
When an object moves in the direction a force is moving it. Whenever work is done energy is transferred: Work done (Joules) = Force (Newtons) x Distance (Metres)
What is the formula for pressure?
Pressure (Pascals) = Force (Newtons) ÷ Area (square metres)
What is the formula for the moment of a pivot?
Moment (Newton metres) = Force (Newtons) x Distance from pivot (metres)
What are the three types of levers?
Class 1: The load and the effort are on opposite sides of the pivot, e.g. pliers and a crowbar
Class 2: The load and the effort are on the same side of the pivot, with the load being closer to the pivot, e.g. nutcrackers and a wheelbarrow
Class 3: The load and the effort are on the same side of the pivot, with the effort being closer to the pivot, e.g. tongs and tweezers
How does a hydraulic system work?
Hydraulics work by having a force applied to one tube of a liquid which has a small surface area. This means that there is a large amount of pressure, which is applied equally throughout the liquid. The other tube is wider, which means it has a larger area. As force = pressure x area, it means a greater force is exerted on the other tube. This makes it a force multiplier
What are two key properties of liquids?
- Pressure exerted on one point of a liquid spreads equally throughout it.
- They are virtually incompressible.
