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|What is displacement s of an object?
|Is the resultant distance moved in a given direction
|Define a scalar quantitiy?
|Has magnitude only
|Define a vector quantity?
|Has magnitude and direction
|how can you find the resultant of two vectors?
|it can be found using a triangle, parallelogram or rectangle to represent them
|What are the components of a vector inclined at and angle of ? to the horizontal?
|horizontal component = V cos ? Vertical component = V sin ?
|How do you find the average speed V of an object?
|How do you find the instantaneous speed of an object?
|the rate of change of distance x: V = ^x/^t
|What is velocity?
|the rate of change of displacement S: a = ^s/^t
|What is acceleration?
|the rate of change of velocity V: a = ^v/^t
|What does the gradient of a displacement-time graph represent?
|velocity: v = ^s/^t
|What does the gradient of a velocity-time graph represent?
|acceleration: a = ^v/^t
|What does the area under a velocity-time graph represent?
|What equation do you use for motion at a constant velocity?
|v = x/t
|What are the equations that are used for motion at constant acceleration?
|V = u + at S = ut + 1/2at^2 S = 1/2(u+v)t V^2 = u^2 + 2as
|How can you describe the horizontal and vertical velocities of a projectile?
|It moves with constant horizontal velocity and a vertical velocity changing due to acceleration due to free fall
|What is the equation that links resultant force on an object to it's mass and acceleration?
|F = ma
|Define the newton.
|A force that gives a mass of 1 kg an acceleration of 1 m/s^2
|What is the equation for weight?
|Weight = mass x gravitational field strength
|Why can't F = ma be used at high speeds?
|Mass increases with energy
|What is viscous drag?
|Objects moving through air or liquids experience air resistance or viscous drag
|What factors does the magnitude of the viscous drag depend on?
|The medium, the size of the object and the speed of the object
|What happens to the viscous drag force when speeds increase?
|It increases with speed
|For an object falling through air explain how an object will reach terminal velocity.
|For a falling object in air under gravity, the drag increases until it equals the weight. The resultant force and acceleration are then zero so the object continues at a constant.
|What is the center of gravity of an object?
|The point where it's whole weight may be considered to act
|Define the moment of a force
|Force x Perpendicular distance from force line to point
|What is a couple?
|A pair of forces that are equal in magnitude but act in opposite directions, producing rotation.
|What is the torque of a couple?
|One force x perpendicular distance between them
|What is the principle of moments?
|For a body in equilibrium, sum of clockwise moments = sum of anticlockwise moments
|What is thinking distance?
|Distance traveled while the driver reacts Thinking distance = reaction time x speed of vehicle
|What is braking distance?
|Distance traveled after brake has been applied. Depends on mass of vehicle and the efficiency of the brakes, and is proportional to the square of the speed
|How do air bags, crumple zones reduce the impact force on a passenger?
|increase the time and distance taken to come to rest so therefore reduce impact forces
|How dopes GPS work?
|Global Positioning Systems use the transliteration technique
|What is work done?
|Force x Distance moved in direction of the force
|Define the joule?
|The energy transferred when a force of 1N moves a distance of 1m in the direction of the force
|What is the conservation of energy?
|Energy cannot be created or destroyed, only changed from one to another
|What is kinetic energy?
|It is equal to the work done in bringing a moving object to rest. 1/2mv^2
|What is gravitational potential energy?
|The rate of working. work done/time taken
|Define a watt.
|It is developed if 1 joule of energy is transferred in a time of 1 second
|Useful energy output / energy input x 100%
|mass per unit volume. m/V Density of water = 1g/cm^3 = 1000kg/m^3
|Force per unit area. F/A Standard atmospheric pressure = 100000N/m^2 = 100kPa
|Describe Hooke's law.
|For a spring or material which is stretched up to it's elastic limit, the extension is proportional to the tension
|Define the spring constant.
|Force per unit extension. F/^x
|Describe elastic deformation.
|Energy is lost and the material is permanently deformed
|What does the area under a force-extension graph represent?
|The work done done in stretching a spring
|White down 2 equations for elastic potential energy.
|1/2F^x = 1/2k^x^2
|Define tensile stress.
|Force per unit cross-sectional area. F/A
|Define tensile strain.
|Extension per unit length. ^x/L
|Define the young modulus.
|Stress/Strain. Young modulus of steel is 2 x 10^11 Pa
|Define ultimate tensile strength.
|The stress at which a material breaks