Forces in Motion Flashcards
Principle of Moments
The sum of the clockwise moments is equal to the sum of the anticlockwise moments.
Centre of Mass
The point through which a single force on the body has no turning effect/a point where all of the object’s mass can be said to act.
Centre of Gravity
An imaginary point at which the entire weight of an object appears to act
Archimedes’ Principle
The buoyant force on an object is equal to the weight of the fluid displaced by the object
Instantaneous speed
The speed of an object at one instant of time
Couple
Two equal and opposite parallel forces that act on an object through different lines of action. It has the effect of causing a rotation without translation.
Newton’s Second Law
The sum of the forces acting on an object is equal to the rate of change of momentum
Projectile Motion
The motion of an object that is fired from a point and then has only gravity acting on it.
Reaction Time
The time taken to process a stimulus and trigger a response to it.
Drag
The frictional force an object experiences when moving through a fluid.
Normal Contact Force
The reaction force between an object and a surface.
Tension
The result of two forces acting on an object in opposite, outward directions
Terminal Velocity
The maximum velocity on an object when the resistive and driving forces are equal to one another.
Calculating average velocity
overall displacement/time
Calculating velocity
Use formulae
How to find when one vehicle overtakes other on v-t graph?
the areas have to be equal. Use equations and equate.
When do you use gradient tangent method on a curve?
When question says ‘estimate’.
How can a skydiver reach maximum speed?
Fall headfirst , arms close to side = streamlined, tightfitting clothes = less drag
How do seatbelts reduce injury?
Stretch a little, so force is reduced, wide area so less pressure on body, holds person in place so they don’t continue moving
What is a moment?
The force multiplied by the perpendicular distance from force to pivot.
What is G.P.E transferred to if not K.E?
Heat due to drag
What is the difference between energy and work done?
Work done is the change in energy, energy is just the base value.
What is a joule?
1 joule is the work done when a force of one newton moves an object through a distance of one metre.
What is power?
energy transferred per unit time
What is work done?
force multiplied by distance moved in direction of force
Why can we not depend on rain for energy?
not big enough area to collect all rain, weather dependent
