# Newtonian Mechanics

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• Newtonian Mechanics
• Newton's First Law
• An object in rest stays in rest and an object in motion stays in motion with the same speed and direction until acted upon by an unbalanced force
• Also known as the Law of Inertia
• If a ball is launched in a vacuum, it will carry on going forever
• Newton's Second Law
• Force is proportional to acceleration (normally) as mass is constant
• If the question is about a rocket and it loses fuel, remember m isn't constant
• F = ma
• Newton's Third Law
• For every action, there's an equal and opposite reaction
• Reaction pairs
• Friction and driving force
• Gravity and the reaction force from the ground
• Gravity and air resistance
• Air resistance and driving force
• SUVAT equations
• v = u + at
• v^2 = u^2 + 2as
• s = ut + 1/2at^2
• a = (u+v)t/2
• Scalar and vector quantities
• Scalar = only magnitude
• Speed
• Mass
• Distance
• Vector = magnitude and direction
• Displacement
• Velocity
• Acceleration
• Momentum = mass x velocity
• Conservation of linear momentum = the momentum doesn't change unless an external, unbalanced force is applied
• m1v1 = m2v2
• Moments
• Moment of a force = Fx
• Where x is the perpendicular distance between the line of action of the force and the axis of rotation
• Also known as torque
• Torque of a couple = Fd
• Where d is the perpendicular distance between the two forces
• Couple = two equal forces which act in opposite directions on an object but not through the same point so they produce a turning effect
• Work and energy
• ?W = F?s
• If the force isn't in line with the motion, resolve the vectors
• Kinetic energy = 1/2mv^2
• Principle of conservation of energy = energy cannot be made or destroyed; only transferred
• P = W / t
• Efficiency = useful energy / total energy
• x100 for percentage
• Gravity
• Gravitational field strength = F / m
• Weight = mg
• g = 9.81 ms^-2