Mechanics Flashcards
What is a force?
Push or pull measured in newtons
What is a vector?
Shows size and direction
What is scalar?
Only shows size
Steps in creating a vector?
- Sketch diagram, 2. Use Pythagoras to calculate unknown vector, 3. Use trigonometry t find unknown angle, resultant force is measured in Newtons with a direction
How to calculate vector subtraction?
V final- V initial
Describe vertical motion under gravity
Decelerate at -9.8 ms-2 when thrown upwards, then at the top of objects path velocity is 0ms-1, then it accelerates downwards at 9.8ms-2
What is the shape of a projectile?
Flight path is parabolic and symmetric
Force acting on object in projectile motion?
Weight force
Why does an object move horizontally at constant speed when in projectile motion?
Because there is no accelerating force in the horizontal direction
What is hookes law?
F=-k x; describes how springs will behave when loads are placed on them
What is Newton’s first law?
An object maintains constant velocity, including stationary, unless acted on by an external net force
What is Newton’s second law?
If an object experiences an external net force, it will accelerate such that f=ma
What is Newton’s third law?
When an object exerts a force on another object, the second object will simultaneously exert a force of the same size and in opposite direction to the force acting on it
The upwards force on a diagram
Support
What causes centripetal acceleration
Velocity is always changing as circular motion is constantly changing direction. This means that there is changing acceleration which is towards the centre of the circle, so force is towards the centre
What direction is an objects velocity in circular motion
At a tangent to the circle
What is torque
A turning force;t=fd
The conditions for an object to be in equilibrium
Sum of torques equal 0; acw force/s= cw force/s
What is a centre of mass
A singular position where an objects weight force acts through
What is gravitational potential energy
Stored energy due to height above ground (measured in J)
What is kinetic energy?
Energy due to movement (measured in joules)
What is the energy stored in spring equation?
Ep=1/2kx^2
Conservation of energy
Energy can not be created or destroyed, ignoring frictional losses
What is the law of conservation of momentum
P before= p after, except when there are external forces acting such as friction
