3.2 Forces in Action Flashcards
If you apply a net force on an object, what will happen?
The object will accelerate in the direction of the net force applied.
What equation relates force, mass and acceleration?
Force (N) = Mass (kg) x Acceleration (ms-2)
What does 1 Newton give?
1 Newton gives 1kg of mass an acceleration of 1ms-2 in the direction of the force.
What is the difference between weight and mass?
Weight is a gravitational force acting on an object - varies with location - and mass is the amount of matter of an object - constant.
How is the weight of an object calculated?
Weight (N) = Mass (kg) x Gravitational force
What device can be used to determine the weight of an object?
A newtonmetre.
What is friction?
The force that arises when two surfaces rub against each other.
What is drag?
The resistive force on an object travelling through fluid (liquid/gas).
What is tension?
The force within a stretched cable or rope.
What is upthrust?
An upward buoyancy force acting on an object when it is in fluid (liquid/gas).
What is a normal contact force?
A force arising when one object rests against another object.
How are forces represented in a free body diagram?
Each force is represented by an arrow labelled with the force, they’re drawn to scale (longer arrow = greater force).
How do you find the vertical component of a force?
mgsinθ
How do you find the horizontal component of a force?
mgcosθ
What is a fluid?
A fluid is a liquid or gas substance.
What is a drag force?
The frictional force that opposes motion of an object.
What is the magnitude of drag dependent on?
- Speed of an object
- Object’s cross-sectional area
How is drag related to speed?
Drag is directly proportional to speed².
Describe how forces of weight and drag change when an object undergoes a vertical fall.
- As the object starts to fall, there is no drag force and acceleration is g.
- As it falls, the speed increases and the drag force increases, resultant force decreases and the acceleration becomes less than g.
- The object will reach terminal velocity, so drag and weight are equal and opposite, speed is constant and the acceleration is 0.
What is the magnitude of drag at the instant an object begins to fall?
Zero.