Force, Motion & Energy Flashcards
Unit 0 Topic 1
What is the difference between distance and displacement?
Distance is the amount of ground traveled whereas displacement is from the starting point to the the finishing point.
What is the different between a vector and a scalar?
Scalar describes a movement by magnitude however a vector describes a movement by magnitude AND direction.
What is the difference between speed and velocity?
Speed is distance/time and is the rate on change in position. Velocity is displacement/time therefore it has direction. s = 3m, v = 3m West
What is the difference between average speed and instantaneous speed?
Average speed is the average rate of change over a period of time. However instantaneous speed is the speed at an exact given moment.
How do you convert km/h to m/s?
km/h — ÷ 3.6 — m/s (x 3.6 opposite way)
How do you find an objects acceleration?
a = (v-u)/t a = (velocity - initial velocity)/time
How do you find velocity, acceleration or distance on a motion graph?
s/t graph = gradient is velocity, area is distance
v/t graph = gradient is acceleration, area is displacement
a/t graph = area is change in velocity
Define equilibrium.
the forces are equal on an object (no net force) therefore there is no change in behaviour.
Explain normal, friction, kinetic and static force.
Normal = perpendicular to the surface the object is in contact with (equal and opposite) Friction = force between to objects in contact Kinetic = friction due to motion Static = friction between stationary objects
What is the different between a FBD and a System diagram?
FBD = a simple diagram with a 2D object and the forces acting upon it SD = Sketch all objects in the situation in more detail
1st Law Explain the Law of Inertia.
If the net force acting on an object is zero, that object will maintain its state of rest or constant velocity. It will only change if an unbalanced force acts upon it.
2nd Law Explain F = ma
The acceleration is directly proportional to the net force and mass.
Force (N) = mass (kg) x acceleration (m/s2)
3rd Law Explain Newtons final law (equal + opposite)
For every action force their is a simultaneous reaction force equal in magnitude but opposite in direction.
How do you find an objects gravitational potential energy?
ΔEg=mgh
mass x gravity x height
How do you find an objects kinetic energy?
Ek= 1/2 mv^2
half x mass x velocity(squared)
ΔEk= 1/2 mv^2 - 1/2 mu^2
Define work (+ equation)
work is energy transferred to an object when a force moves it a distance (joules)
work = fs (force x displacement)
work = fscos(theta)
work = ΔE
When will the work being done on an object be zero?
displacement or force = zero
If ‘f’ is perpendicular to ‘d’
Why is an energy transfer never 100% efficient?
Some of the energy can be transferred into a place it doesn’t want to go.
How do you calculate efficiency?
%efficiency = (energy out/ energy in) x 100 %efficiency = (height 2/ height 1) x 100
What is the formula for power?
P = ΔE/Δt P = W/Δt
What is the difference between momentum and impulse?
momentum is the product of an objects mass and velocity
- p = mv
impulse is the change in momentum
- I = Δp = mv - mu
What is the difference between elastic and inelastic collisions?
An elastic collision has no loss of kinetic energy whereas and inelastic collision will have a portion of energy loss
