click below
click below
Normal Size Small Size show me how
Mechanics (physics)
Question | Answer |
---|---|
Define scalar | A quantity with magnitude but no direction |
Define vector | A quantity with magnitude and direction |
Give 6 examples of scalar quantities | -Distance -Speed -Mass -Energy -Volume -Charge |
Give 6 examples of vector quantities | -Displacement -Velocity -Force -Acceleration -Momentum -Torque |
What does a horizontal line mean on a distance time graph | Stationary |
What does a straight diagonal line mean on a distance time graph | Constant velocity |
What does a concave curve mean on a distance time graph | Accelerating |
What does a convex curve mean on a distance time graph | Decelerating |
Define velocity | Rate of change of displacement |
Define speed | Rate of change of distance |
Define momentum | Product of mass and velocity |
Define acceleration | Rate of change of velocity |
What are the 4 suvat equations | ->v=u+at ->x=((u+v)/2)t ->v^2=u^2+2as ->x=ut+0.5at^2 |
How is v=u+at derived | y=mx+c |
How is x=((u+v)/2)t derived | Area under a graph |
How is v^2=u^2+2as derived | -Combining v+u+at and x=((u+v)/2)t -To eliminate t |
How is x=ut+0.5at^2 derived | -Combining v+u+at and x=((u+v)/2)t -To eliminate v |
How does velocity vary before parachute is deployed and why? | -W acts down -Initially AR=0 -Resultant acts down -Therefore accelerates down -As V increases AR increases -Until AR and W are balanced forces -ΣF=0 then because F=ma(Newtons 2nd law) there is no acceleration -Terminal velocity is reached |
How does velocity vary after parachute is deployed and why? | -W remains constant, acting down -Parachute being deployed causes AR to massively increase -Resultant is a large upward acting force -Therefore decelerates down -As V increases AR decreases by ever decreasing amounts -Until W and AR are balanced |
Define average speed | Distance covered in a certain time divided by that time |
Define speed | Rate of change of distance |
Define average velocity | Change in displacement in a certain time divided by that time |
Define average acceleration | Change in velocity over a certain time divided by that time |
Define inertia | A body's reluctance to changing its velocity |
Define force | That which changes an objects state of rest, or of uniform motion in a straight line |
What is the equation linking power, force and velocity | P=Fv |
What is Newtons 1st law | A body that is a rest or at constant velocity will remain at rest or constant velocity unless acted on by a resultant force |
What is Newtons 2nd law | When a force acts on a body, the rate of change of momentum is directly proportional to the force and takes place in the direction of that force |
What is the equation for newtons 2nd law | ΣF=ma |
What is the equation for weight | W=mg |
What is the equation linking force and momentum | F=(m(v-u))/t |
What is the equation for wind hitting wall and hosepipe hitting cat | F=A(u^2)ρ |
What is the equation for jets from a rocket and helicopter lift | F=A(v^2)ρ |
What is newtons 3rd law | If body A exerts a force on body B, body B will exert a force of the same type that is equal in magnitude and opposite in direction on body A |
What is the criteria for Newtonian pairs | -Same type of force -Act on different bodies -180° apart -Same magnitude |
Define impulse | The force applied multiplied by the time for which that force is being exerted |
What are the units of impulse | Newton-seconds (Ns) |
What are the criteria for a free body diagram | -1 body -Forces come from same point -Can be different types |
Define centre of mass | Single point where all mass can be modelled to be found |
Define centre of gravity | Centre of mass for a heterogeneous material |
What must we do when calculating moments | Split into clockwise and anticlockwise |
Define topple | When a line drawn vertically from the centre of mass falls outside the base area |