# SP1 Motion

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## SP1a Vectors and Scalars

• All forces have both a magnitude (size) and a direction, and are measured in newtons (N).
• Vector quantities - quantites that have size and direction. Forces are vectors.
• Scalar quantites - quantities that only have size, examples include distance, speed, energy and time.
• Displacement is the distance covered in a straight line
• The speed - how far an object moves in a certain time
• Velocityspeed in a particular direction.
• Acceleration - a measure of how fast velocity is changing.
• Momentum - a combination of mass and velocity.
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## SP1b Distance/Time Graphs

• Speed (m/s) = distance (m) ÷ time (s)
• Calculated usng light gates - more accurate.
• Adverage speeds for: walking - 1.4m/s, cycling - 6 m/s and train - 55m/s.
• WInd - 5-20m/s and sound in air - 340m/s

Distance/Time Graph:

• Horizontal lines: object stationary
• Straight lines: constant speed
• Steep lines: faster constant speed
• Curves: acceleration
• Gradient: the speed of the object
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## SP1c Acceleration

• Acceleration - change in velocity , units are m/s ² and is a vector quantity.
• accleration (m/s²)= change in velocity (m/s) ÷ time (s)
• a = (v - u) ÷ t (v - final velocity, u - intial veloctiy)
• (final velocity)² - (initial velocity)² = 2 x acceleration x distance
• v²-u²= 2ax
• If there are no forces acting on a object in free fall, the acceleration due to gravity is 9.8m/s² or 10m/s².
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## SP1d Velocity/Time Graphs

On a velocity/time graph:

• horizontal lines: constant velocity
• sloping lines: accelerating (steeper the line, greater the acceleration)
• line below horizontal axis: negative velocity (object moves opposite direction)
• area under a velocity/time graph: distance travelled (distance= velocity x time/ base x height)
• if the object is accelerating (sloping line), split the shape into a triange (area = 0.5 x b x h) and rectangle and find their areas separately.
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