Mechanics Flashcards
What is the equation of work done?
Work done = force x s x cos angle between force and displacement
-force x distance in which the force is applied
What is the equation for elastic potential energy?
Force x displacement (or extension)
What is energy?
Always conserved!
-Ek = Ep = Eg
What is an equation for power?
- Power = energy / time
- Power = force x velocity
- Power = work done / time
What is Newton’s third law?
When body A exerts a force, F on body B, body B exerts an equal and opposite force, F on body A
-Every force has a paired equal and opposite force
What is Newton’s second law of motion?
When an unbalanced (or resultant) force acts on a body, it will accelerate in the direction of that force. The size of the acceleration may be determined by using the equation F = ma
What is Newton’s first law?
A body will remain at rest or continue to move in a straight line with a constant velocity unless it is acted on by an unbalanced force
What is the centre of mass?
The point in a body around which the resultant torque due to the pull of gravity is zero
What is the principle of moments?
Objects in equilibrium when sun or anti-clockwise moments is equal to sum of clockwise moments
How do you work out a moment?
Turning moment = force applied x perpendicular distance from pivot
What is a couple?
- A pair of equal and opposite coplanar forces
- A pair of forces that provide a turning effect but no translational movement
- Act in opposite fires thin and are parallel but do not not act along the same line
How is a moment of a couple defined?
Force x perpendicular distance between the lines of action of the forces
Difference between scalar and vector?
- Scalar only magnitude
- Vector magnitude and direction
What is momentum what are the units?
momentum = mass x velocity (kgms-1), kg, ms-1
How is momentum conserved?
total momentum before collision = total momentum after collision
What are the two types of collision?
- Elastic: where momentum and kinetic energy is conserved i.e.i no energy is dissociated as heat, sound etc
- Inelastic: some of kinetic energy is converted into other forms during collision but momentum is always conserved
What is force?
- Rate of change in momentum
- F=delta(mv) / deltat
What is impulse?
- impulse = change in momentum
- Ft = mv-mu
- The area under a force time graph
How can you reduce impact?
- Crumple zone: the parts at the front of the car crumple up on impact, this causes the car to take longer to stop, increasing the impact time and so decreasing the force on the passengers
- Seat belts: these stretch slightly, increasing the time taken for the wearer to stop. this reduced the forces acting on the chest
- Air bags: these also slow down passenger more gradually and prevent them from hitting hard surfaces inside the car
What is the centre of mass?
- point at which all the objects weight acts
- all the mass of the object appears to be concentrated at the centre of mass
