Mechanics

• If no resultant force, there is no acceleration
• energy, mass, speed and distance are scalar
• Displacement, velocity, acceleration, force and momentum are vectors
• Work done is the energy transferred by a force
• Work done = force x distance
• power developed is the rate at which work is done on an object
• Power developed = force x velocity
• Work = force x distance (cos x ) when x is the angle of which the force is applied
• Newton’s first law

  If no resultant force acts in an object its motion will be constant (no acceleration)
• Newton’s second law

  F = ma
• Newton’s third law

  For ever action (force) there is an equal and opposite reaction (force) which is why momentum is conserved
• if object on a slope is stationary or velocity is constant, there must be an equal and opposite force pulling the object back up the slope (friction)
• On a slope, If no frictional forces, GPE at the top = KE at the bottom
• If there is frictional forces on the slope, GPE = KE + (Work done x d) (where d is the length of the ramp)
• S = ut + 1/2 at^2
• v^2 = U^2 + 2as
• V = U + at
• S = u + v / 2 (t)
• If objects motion ends in the original position, s=0 and it’s useful for problem to be split into half by going to the apex to begin with (top of curve where v=0)
• For projectile motion, resolve vertically (SUVAT) and horizontally (SUT). Vertically a = 9.81.
• For projectile motion at an angle, split the initial velocity into components
• momentum is always conserved
• M1U1 = m1v1 + m2v2
• P = m v
• if acceleration is constant, use SUVAT equations
• Displacement is the area of a velocity time graph
• Gradient of a velocity time graph is the acceleration
• Displacement time graph gradient is velocity
• Frictional forces convert kinetic energy into other useless forms
• Terminal speed occurs when frictional and driving forces are equal, no acceleration and the velocity is constant.
• Terminal velocity is the constant speed reached after falling, weight begins greater than resistance. as speed increases, resistance increases, continues until weight and resistance become equal.
• When air resistance is present, maximum height is reached earlier and horizontal distance decreases
• Impulse is the change in momentum
• Force time graph area is impulse
• Impulse

  F x t = mV- mu
• Elastic collision is when momentum and kinetic energy are conserved
• Inelastic collisions are where only momentum is conserved, kinetic energy is NOT conserved and will be lost to surroundings
• If objects stick together after collision

  inelastic collision
• explosion is a type of inelastic collision as the kinetic energy is greater than before the collision
• Elastic collision is when the objects begin and end apart