Chapter 3.2 - Forces in Action Flashcards
Equation for weight
W=mg
Tension
A force experienced by a string or wire that is being pulled
Normal contact force
A force that acts perpendicular to the point of contact between two surfaces
Upthrust
The upward force that a liquid or gas exerts on a body due to the liquid or gas being displaced
Friction
A force that occurs between two surfaces that opposes motion. It is a result of intermolecular forces.
What you show on a free body diagram (3)
- The bodies
- The directions of each force
- The value of each force
Fluid
A liquid or a gas
Drag
The frictional force experienced by an object travelling through a fluid
Does friction depend on velocity
no sir
Does drag depend on velocity
o yes
How is drag related to velocity
D = kv^2
Factors affecting drag (4)
- Density of fluid
- Coefficient of drag
- Cross sectional area of object
- Velocity
The motion of an object falling in the presence of drag
- Initially accelerates because force of gravity acts downwards and there is minimal drag
- As speed increases the upwards force of drag increases
- Eventually the force of weight is equal to the force of drag and the object no longer accelerates and is moving at its terminal velocity
What happens when a parachute is opened while falling at terminal velocity
The drag force increases due to the increased cross sectional area. This results in a net upwards force and therefore an upwards acceleration, which causes the skydiver to slow down. As they slow down the drag force decreases until a new terminal velocity is reached
Terminal velocity
The speed of an object at which the weight is equal to the drag