Forces Flashcards
What is resultant force?
The overall force on a point or object
What is Work Done?
When a force moves an object through a distance, (energy is transferred)
When is an object at equilibrium?
When all the forces acting on an object are balanced
When you apply a force to an object you can cause it to?
stretch, compress or bend
(this transfers energy/ work is done)
What does it mean if an object is inelastically deformed?
the object won’t return to its original shape/length after the force on it is removed.
What is the relationship between force and extension
Force is directly proportional to Extension
What does a stiffer spring do to the spring constant?
Gives it a greater spring constant
What is the Limit of Proportionality?
When spring extension is no longer proportional to force
What are fluids?
substances that can flow as their particles can move around
What does pressure of a fluid mean?
Pressure is exerted at normal (right angles) to surfaces in contact with the fluid
What is Density?
The measure of how compact particles in a substance are.
What is the difference between the density of a liquid and the density of a gas?
Liquid: density is uniform/same everywhere
Gas: varies with height
How does density affect pressure in terms of particles?
A higher density means more particles in a given volume, more particles are able to collide-> higher pressure
How does depth affect pressure in terms of particles?
As depth increases, number of particles above increases-> weight adds more pressure
What equation is pressure in a column?
Pressure= hpg
height of column of liquid
Gravitational field strength
Density of liquid
What is Upthrust?
A resultant force equal to the weight of the fluid displaced by the object
What happens to an object if its upthrust is equal to its weight?
The forces balance and the object floats
What happens to an object if its weight is more than its upthrust?
The object will sink
What does density dictate about an object?
Whether it will float or not
When will an object float?
When the object is less dense than the fluid it’s placed in
What is the relationship between Atmospheric pressure and Height/Altitude ?
Atmospheric pressure decreases as height (from sea level) increases
What is Atmospheric pressure?
Created on a surface by air molecules colliding with the surface
Why does pressure decrease as altitude increases?
Air becomes less dense, less particle collisions
Also fewer air molecules above, weight decreases
What is Friction?
Force that acts in the opposite direction of movement
If speed increases, what happens to drag?
Drag also increases
What is drag?
resistance in a fluid
How do you reduce drag?
- keep the object’s shape streamlined
What is Terminal Velocity?
When the acceleration of a falling object and its drag are the same (resultant force = 0)
- the object falls at a constant speed
What is Terminal Velocity determined by?
- Drag in comparison to Weight
- Shape
- Area
What is the equation for Stopping distance?
Stopping distance= Thinking distance + Breaking Distance
What is Stopping distance?
the distance it takes to stop a car in an emergency
What is Thinking distance?
how far the car travels during the driver’s reaction time
What is Breaking distance?
distance taken to stop under a breaking force
What is Thinking distance affected by?
- Speed
- Reaction time
What is Breaking distance affected by?
- Speed
- Weather or Road surface (wet or icy, leaves or oil on the road)
- Condition of the tyres (less tread, skidding)
- Condition of brakes (faulty, worn etc)
What causes a car to brake, between the brakes and the wheels?
Friction
- brake pads pressed on wheels
What are the dangers of driving fast and then braking?
- faster a car is going, more energy in kinetic stores, more works need to be done to stop-> greater braking force
- large braking force-> larger deceleration, causes brakes to overheat + cause vehicle to skid
What factors affect Reaction time?
- tiredness
- drugs
- alcohol
- distractions (music, on the phone)
Why are speed limits important?
- Speed seriously affects stopping distance, reduces amount of likely accidents
What affects braking distance the most?
Speed
