Forces Flashcards
What is displacement?
Distance in a given direction
What is a vector quantity?
A quantity with magnitude and direction
What is a scalar quantity?
A quantity with magnitude only
Examples of vectors
- Displacement
- Force
- Velocity
- Weight
- Momentum
Examples of scalars
- Distance
- Speed
- Time
- Mass
- Energy
- Power
What is Newtons Third Law of Motion?
When two objects interact with each other, they exert EQUAL and OPPOSITE forces on each other
What is the resultant force?
The single force that has the same effect as all the forces acting on the object, the overall force
What is Newton’s First Law of Motion?
An object will remain in motion at constant speed in a given direction until acted upon by an external force
What is a moment?
The measure of the turning effect of a force on an object
Equation of a moment
M = FD
Moment = Force x Perpendicular distance from line of action to the pivot
What does a lever do?
Acts as a force multiplier meaning less of an exerting force is required to move an object
What do gears do?
Act as a force multiplier
What does a low gear do?
Gives low speed and a high turning effect
What do high gears do?
Give a high speed and low turning effect
What is the principle of moments?
If an object is in equilibrium about a pivot, the anticlockwise and clockwise forces about the pivot are equal
What does the gradient of a distance-time graph represent?
The speed
What is the equation for acceleration?
a = (v-u) / t
What does the gradient of a velocity-time graph represent?
Acceleration
What does the area under a velocity time graph represent?
Displacement
What equation links velocity, distance and acceleration?
V^2 = U^2 + 2as
Equation for Force
F = MA
What is Newton’s Second Law of Motion?
The acceleration of an object is proportional to the resultant force acting on it.
Acceleration is also INVERSELY PROPORTIONAL to the mass of an object
What is inertia?
An object’s tendency to remain in rest or in motion unless acted upon by an external object
What is terminal velocity?
When the resultant force on an object is 0, so the object stops accelerating and moves at a constant velocity
Stopping distance
The distance a car travels during the sum of the thinking and braking distance
Braking distance
The distance a car travels under the braking force
Thinking Distance
The distance a car travels during the driver’s reaction times kicking in
What is the equation for momentum?
P = MV
Momentum = Mass x Velocity
What is the law of conservation of momentum?
In a closed system, the total momentum before an event is the same as the momentum after an event
What is the equation for impact force?
Impact force = change in momentum / time
What are some safety measures to reduce impact force?
- Airbags
- Seatbelts
- Crumple zones
- Cushioned playground surfaces
What is Hooke’s Law?
The extension of a spring is directly proportional to the force applied to it.
This rule applies until the ‘limit of proportionality’ is reached, where the spring has been stretched too far.
What is the equation for Hooke’s Law?
F = ke
What is the spring constant?
The stiffer the spring, the greater the spring constant
centre of mass
The point at which the weight of the object acts
