#### Transcript Linear Motion

Biomechanics • Mechanics of movement: – vectors and scalars – velocity, acceleration and momentum/impulse in sprinting – Newton’s Laws applied to movements – application of forces in sporting activities – projectile motion – factors affecting distance, vector components of parabolic flight – angular motion – conservation of angular momentum during flight, moment of inertia and its relationship with angular velocity. Using ‘Newton’s First’ and ‘Second Laws of Motion’, explain how the swimmer dives off the starting blocks. (4 marks) 4 marks for 4 of: • A. Force is applied by the muscles Newton’s First Law of Motion/Law of inertia • B. Performer will remain on the blocks unless a force is applied • C. Performer continues to move forwards with constant velocity until another force is applied • D. Water slows the swimmer Newton’s Second Law of Motion/Law of Acceleration • E. Mass of swimmer is constant • F. Greater the force exerted on the blocks, the greater the acceleration/momentum • G. Force governs direction (something WILL come up on this subject!) Biomechanics The term ‘Biomechanics’ literally means ‘the mechanics of living beings’ and it is used to analyse human performance from a scientific standpoint with the aim of: • achieving optimal sporting techniques, • improving the design of equipment • determining the stresses imposed on the body during performance in order to prevent injury. Linear Motion • Occurs when a body moves in a straight or curved line with all parts of the body moving the same distance in the same direction at the same speed. • We are going to cover the following aspects of linear motion: Vectors Speed Acceleration Scalars Velocity Force Mass Distance Inertia Weight Displacement Momentum Vectors and scalars Scalar Quantities – are only considered in terms of their magnitude Vector Quantities – are considered in terms of magnitude and direction E.g. a man is walking at 2km/h = ?? Scalar A man is walking north-east at 2km/h = ?? Vector Mass and Weight Mass – is the amount of matter (‘stuff’) that something is made up from Scalar It is measured in Kg Weight – Is the force exerted on the mass of a body by gravity. Vector It is measured in Newtons (N) Weight = mass x acceleration due to gravity On Earth, acceleration due to gravity is ~ 10 m/s2… Are mass and weight scalar or vector quantities? … so weight is 10x mass! Force Force is the ‘push or pull’ exerted on an object or body, which may either cause motion of a stationary body or a speeding up, slowing down or change of direction of a moving body. Force can be generated internally by Muscle contraction or externally by Gravity, friction, water and air resistance Without such forces, movement would not be possible, and when such forces are understood and adapted to the same aim, optimal performance can be achieved. Force is a Vector quantity – what does this mean? It has magnitude and direction. Often, more than one force is acting upon an object. The resultant force can be calculated by either adding the forces in the same direction; subtracting the forces in opposite directions, or by constructing a parallelogram of forces with the resultant force lying on the diagonal of the parallelogram. Draw arrows to show the resultant force from the following vectors: a) d) b) e) c) f) Linear Motion • Occurs when a body moves in a straight or curved line with all parts of the body moving the same distance in the same direction at the same speed. • We are going to cover the following aspects of linear motion: Vectors Speed Acceleration Scalars Velocity Force Mass Distance Inertia Weight Displacement Momentum Speed and Velocity When analysing sporting performance, we are always concerned with how fast a body or an object is – i.e. their speed Is speed a scalar or vector quantity? Distance travelled (m) Speed = Scalar Time taken (s) 1. Calculate the speed (m/s) of a person who jogged 600m in 2 minutes 2. Calculate the distance (m) a man would travel in 3 minutes running at a speed of 4 m/s 3. Calculate the time it would take a woman to swim 400m at a speed of 1.6m/s 1. Calculate the speed (m/s) of a person who jogged 600m in 2 minutes Speed = D/T = 600 / 2x60 = 600 / 120 = 5m/s 2. Calculate the distance (m) a man would travel in 3 minutes running at a speed of 4 m/s Distance = SxT = 4 x (3x60) = 4 x 180 = 720m 3. Calculate the time it would take a woman to swim 400m at a speed of 1.6m/s Time = D / S = 400 / 1.6 = 250s Speed and Velocity Velocity is a Vector quantity – what must it have that Direction speed doesn’t? Velocity = Displacement (m) Time taken (s) Displacement is the shortest possible route between the starting and finishing point – normally measured in a straight line (as the crow flies) in metres (m) As velocity is a vector, directional information is needed to fully describe it. i.e the car travelled with a velocity of 30mph in a south-westerly direction. Look at page 82 of the textbook to see the distance and displacement of the great north run compared. Acceleration (and deceleration) Is acceleration a scalar or vector quantity? Vector I.e. it is the rate of change of velocity of an object. -1) Change in Velocity (ms Acceleration = Time (s) We tend to think of it as how quickly an object is speeding up, or slowing down. Acceleration should be stated with a direction e.g. the sprinted accelerated at 5ms-2 towards the finish line The high jumper accelerated upwards at 8ms-2 The Acceleration (or deceleration) of an object can be shown through the gradient of a velocity-time graph. Figure 2 shows a velocity/time graph for an elite 100-metre sprinter. (i) Use Figure 2 to determine the velocity of the sprinter after 3 seconds, and identify the period of time when the sprinter’s acceleration was the greatest. (2 marks) (ii) What is happening to the sprinter between 6 and 11 seconds? Explain why this occurs. (3 marks) (b) (i) 1. 9.1 ms-1 (accept 9.0-9.2); 2. 0-1 seconds. 2 marks (ii) 1. Deceleration/decrease in velocity; (Do not credit slowing down) 2. Lack of ATP; 3. CP breakdown to ATP slowing/limiting; 4. Due to lack of stored PC; 5. Change to slower lactic acid/ alactic/anaerobic system 3 marks Linear Motion • Occurs when a body moves in a straight or curved line with all parts of the body moving the same distance in the same direction at the same speed. • We are going to cover the following aspects of linear motion: Vectors Speed Acceleration Scalars Velocity Force Mass Distance Inertia Weight Displacement Momentum Inertia • Inertia is the reluctance of a body to move or change its state of motion • Objects will stay in their state of inertia (i.e. stationary or moving at a constant velocity) unless a force overcomes that inertia. •The inertia of a body is directly proportional to its mass • Therefore an object with a greater mass requires a larger force to overcome its inertia and change its state of motion. Momentum • Momentum is the amount of motion a body has • Momentum is calculated as: Mo = Mass (kg) x Velocity (ms-1) • The more massive, or the faster an object, the more momentum it has. • Momentum is linked to inertia – the more momentum something has, the harder it is to stop! Ben Morgan 1m 93 117 kg Leigh Halfpenny Richie Gray 2m 08cm 120 kg 1m 78cm 83 kg What is each of their momemtum when running at 4ms-1 Prep Definitions sheet Task 5.02 and 5.05. MyPEExam- A2 Vectors and Scalars + Newtons Laws of Motion