Forces Flashcards
What is a vector quantity?
Quantities with a magnitude and a direction (e.g. force, velocity, displacement).
What is a scalar quantity?
Quantities with a magnitude but no direction (e.g. speed, distance, mass).
What is gravitational force?
The force of attraction between masses.
What equipment can you use to measure weight?
A calibrated spring balance (or newtonmeter).
What is “work” done?
The exertion of force overcoming resistance whilst transferring energy.
When a force moves an object through a distance…
When a force moves an object through a distance, energy is transferred and work is done on the object.
What is an elastic object?
An object that can be elastically deformed, the object can go back to its original shape and length after an applied force has been removed.
What is the limit of proportionality?
The point at which extension is no longer proportional to force.
What is a moment?
The turning effect of a force.
What is the effect of levers?
Levers increase the distance from the pivot at which the force is applied. Since M = Fd this means less force is needed to get the same moment. This means levers make it easier to do work (e.g. lift a load or turn a nut).
What are gears and their function?
Gears are circular discs with ‘teeth’ around their edges. Their teeth interlock so that turning one causes another to turn, in the opposite direction. They are used to transmit the rotational effect of a force from one place to another.
How does the size of a gear affect the moment?
Different sized gears can be used to change the moment of the force. A force transmitted to a larger gear will cause a bigger moment, as the distance to the pivot is greater. The larger gear will turn slower than the smaller gear.
As the depth of a liquid increases…
As the depth of a liquid increases, the number of particles above that point increases. The weight of these particles adds to the pressure felt at that point, so liquid pressure increases with depth.
Describe how objects in fluids experience upthrust.
When an object is submerged in a fluid (either partially or completely), the pressure of the fluid exerts a force on it from every direction.
Pressure increases with depth, so the force exerted on the bottom of the object is larger than the force acting on the top of the object.
This causes a resultant force upwards, known as upthrust.
The upthrust is equal to the weight of the fluid that has been displaced by the object.
Why does atmospheric pressure decrease as altitude increases?
As the altitude increases, the atmosphere gets less dense, so there are fewer air molecules that are able to collide with the surface. There are also fewer air molecules above a surface as the height increases. This means the weight of the air above it, which contributes to atmospheric pressure, decreases with altitude.
