Mechanics concerns objects and systems - their forces and displacements.
Kinematics is a branch of mechanics that doesn't concern forces.
In kinematics, the SUVAT equations exist to make calculations easier, providing that the object is in uniform acceleration at all times.
You can rearrange the formulae in any way you want to get the values that you may need.
The best way to understand the formulae is to simply use diagrams. In "a = (v-u)/t", the acceleration is the gradient of the velocity-time curve. So when v = u + at is the curve, it looks just like y = mx+c, where m is the gradient (acceleration), x is the time, and c is the offset (u).
However, for the displacement-time curve, it is a bit more complex because it is a quadratic formula: s = ut + frac(1,2)*at2 is just like y = bx + ax2. This means that you can work with the fundamental formula of kinematics mathematically.
This is in M1 of Mathematics.
The gradient of a displacement-time curve is the velocity. The gradient of a velocity-time curve is the acceleration. That means that you have to differentiate the displacement formula to find out the velocity. To get the acceleration from a displacement-time curve, you will have to differentiate twice.
The opposite happens if you want to find out the velocity from acceleration or even displacement from acceleration - you have to use integration.
1D motion is really useless. It is much more useful to learn motion in 2D. Basically, in 2D, vectors will have two components - vertical, and horizontal. Everywhere in mechanics you will have to understand the horizontal and vertical components, both in M1 and in Forces and Motion modules of Mathematics and Physics respectively.
You may see two velocities acting on an object - 15ms-1 vertically and 15ms-1 horizontally, resulting in 21 ms-1 totally:
This does make sense, but mainly, when trying to understand, you should draw a vector triangle, where each velocity acts at eachother's end. Same applies to force diagrams:
This is a simple force diagram - an object has a northwards force acting on it at 15 N and another force 21.21 N north-eastwards from the first force's endpoint. Calculate the total force:
Here, you just split up the forces into the components and then add them up:
Simple!:)
Force (Newtons) = Mass (kilograms) * Acceleration (metres per second squared)
Force (N) = Mass (kg) * Acceleration (ms-2)
This is the second Newton's law - the total force on an object is proportional to the rate of change of momentum (momentum = mass * velocity)
Tension is a basic force in a string or an object that is pulled. Tensions are measured in Newtons, just like normal forces
A moment is the turning effect created by an object. A pivot can be anything - a door's side, a real pivot or just a chair
Moment of a force (Newton metres) = Force (Newtons) * Perpendicular distance from the pivot (metres)
Moment = Fx
A crucial point is the 'perpendicular' distance from the pivot - the distance that the force *really* has an effect.
Imagine attaching a string to the handle of the door. It would be the easiest if you pull the string exactly in the front of the door because the perpendicular distance from the pivot is the largest. Now, if you take that string and pull it at a 30 degree angle from the handle, it will take more force to do the same - the perpendicular distance has changed. The real effective length, if the door is 1m wide, will be the same as if pulling at 90 degrees from the middle of the door because of the perpendicular distance being 1 * sin30 = 0.5m.
Safety in cars can be provided in a number of ways: air bags, seat belts and the crumple zone. These methods tend to get rid of some of crash energy that can injure the passengers.
The crumple zone is a zone (usually in the front of the vehicle) that tends to absorb crash energy.
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