1.3 & 1.4 Forces and Pressure Flashcards
What is friction?
A force opposing motion when both surfaces are solid.
What is drag?
a force opposing motion when one surface is a fluid.
What is Hooke’s Law?
When a force changes a spring’s shape, the spring’s extension is directly proportional to the force.
Force(N) = Spring constant (N/m) x Extension (m)
What do forces do?
1. Change an objects speed
2. Change an objects direction
3. Change an objects shape
(Acceleration)
What is a moment?
The moment is a measure of a forces ability to rotate an object about a pivot (the turning effect of a force).
moment (Nm) = force (N) x perpendicular distance from pivot (m)
What is the Law of Moments?
When an object is in equilibrium the sum of the clockwise moments is equal to the sum of the anticlockwise moments.
What is the centre of gravity?
The point where all the weight of an object seems to act through.
What is a fluid?
A substance with no fixed shape, like a gas or liquid.
How do you calculate fluid pressure?
Fluid pressure (N/m^2) = force (N) ፥ Area (m^2)
What is atmospheric pressure?
The air all around us that exerts a pressure on our body all the time.
When will an object float?
An object will float if its density is less than waters density and if the objects weight is equal to the upthrust (the size of the upthrust will be equal to the weight of the water it displaces)
What is the formula for weight (on Earth)?
weight (N) = mass (kg) x gravity (10N/kg)
How do you calculate density?
Density (kg/m^3) = mass (kg) ፥ volume (m^3)
How do you calculate pressure?
pressure (N/m^2) = force (N) ፥ area (m^2)
