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PE A-Level Mrs Rex > Biomechanical Movement: Linear Motion > Flashcards

Biomechanical Movement: Linear Motion Flashcards

Liner Motion

1
Q

What is linear motion?

A
  • Motion in a straight or curved line with all body parts movinh at the same speed in the same direction.
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2
Q

What is a scalar quantity?

A
  • A quantity that has magnitude
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3
Q

What is a vector quanitity?

A
  • A quantity that has both magnitude and direction.
  • Usually represented by arrows. The length of the arrow shows magnitude. Longer the arrow, the bigger the size. Direction is shown by line of application
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4
Q

What is mass?

A
  • Physical quanitity of matter/substance in a body.
  • Made of bone, muscle, tissue and fluid.
  • Measured in kg
  • Mass is scalar
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5
Q

What is weight?

A
  • Force on a given mass due to gravity.
  • Measured in Newtons (N)
  • Weight = mass x gravity
  • Weight is a vector.
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6
Q

What is distance?

A
  • The path a body takes as it moves from the starting to finishing position.
  • Measured in Metres (m)
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7
Q

What is displacement?

A
  • Shortest rate in a straight line between startig and finishing position.
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8
Q

What is speed?

A
  • The rate of change of a position
  • Speed (m/s) = distance covered (m) / time taken (s)
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9
Q

What is velocity?

A
  • How fast a body travels in a certain direction.
  • The rate of change of displacement.
  • It’s a vector
  • Velocity = displacement (m) / time (s)
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10
Q

Distance time graphs: Stationary

A
  • Line doesnt go up or down.
  • No distance travelled
  • Performer is stationary
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11
Q

DIstance time graphs: Constant speed

A
  • Constant diagonal direction.
  • Distance run is changing at a constant rate and at the same speed.
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12
Q

Distance time graph: Acceleration

A
  • Curve gets gradually steeper.
  • More distance covered in a certain amount of time
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13
Q

Distance time graph: Deceleration

A
  • Curve levels off
  • Less distance covered in a certain amount of time.
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14
Q

Velocity time graph: Constant velocity

A
  • Gradient remains constant, indicates performer is travelling a constant velocity.
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15
Q

Velocity time graph: Acceleration

A
  • Gradient gets steeper, indicates performer is moving with increasing velocity.
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16
Q

Velocity time graph: Deceleration

A
  • Gradient decreases, indicates performer is mocing with decreasing velocity.
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17
Q

Velocity time graph: change in direction.

A
  • As curve goes below the X axis, the performer has changed direction
18
Q

What is acceleration?

A
  • The rate of change of velocity.
  • When velocity increases, positive acceleration occurs.
  • when velocity decreases, negative acceleration occurs.
  • It’s measured in m/s/s
  • Acceleration = change in velocity/time
  • Change in velocity = (final - initial)
19
Q

What is momentum?

A
  • Product of mass and velocity of an object.
  • Momentum (kg/s) = mass (kg) x velocity (m/s)
  • It is a vector
  • If mass/velocity increases, so will momentum.
20
Q

Conservation of momentum.

A
  • It can be conserved
  • Occurs when performer of object is in flight.
  • When in flight neither mass nor velocity can be altered
  • Mass is constant (unchanged)
  • Velocity can only be altered by external forces such as gravity and air resistance.
21
Q

What are the forces acting on a performer during linear motion?

A
  • A force will change a body’s state of motion
  • There are two types of forces: internal/external
22
Q

What are internal forces?

A
  • Generated by skeletal muscle.
  • E.g. dunk in basketball, the force is generated in the gastrocnemius, quads and gluteals that contract concentrically to plantarflex the ankle and extend the knee and hip in a jump.
23
Q

What are external forces?

A
  • Comes from outside the body
  • E.g. friction, air resistance and weight
  • Gravity is an external force but is described as weight.
24
Q

How can external forces be categorised?

A
  • Vertical forces: gravity/weight and reaction
  • Horizontal forces: friction and air resistance
25
Q

What are vertical forces?

A
  • Weight: graviational force that the earth exterts on a body, pulling it down.
  • The greater the mass the greater the weight force pulling it down.
  • Reaction force: whatever the force acting on a performer during linear motion, a reaction force will be generated.
  • Newtons 3rd law states that ‘for every action there is an equal and opposite reaction’.
26
Q

What are horizontal forces?

A
  • Friction: ‘Opposite motion’ and ‘Occurs when 2 or more bodies are in contact’
  • Two types of friction: static and sliding
  • Air resistance: force that acts in the opposite direction of the motion.
27
Q

What is static friction?

A
  • Force exerted when there is no motion between 2 surfaces
  • This is dry friction, it acts between 2 surfaces that are not moving.
28
Q

What is sliding friction?

A
  • Force exterted when there is motion between 2 surfaces.
29
Q

What is friciton affected by?

A
  • Roughness of a surface: rougher the surface, the greater the friction
  • Mass of an object: greater the mass, the greater the friction
  • Temperature of surfaces: increase in temperature, reduce friction.
30
Q

What is air resistance affected by?

A
  • Velocity of the mocing body
  • Frontal-cross section area of moving body
  • Shape/surface characteristics of moving body
31
Q

What is net force?

A
  • Resultant force acting on his body when all other forces have been considered
  • It’s often discussed as balanced/unbalanced forces.
32
Q

Free body diagrams: weight/reaction

A
  • Weight: force drawn down from the centre or mass
  • Reaction: a force that starts from where 2 bodies are in contact.
33
Q

Free body diagrams: friction/air resistance

A
  • Friction: a force starts from where the 2 bodies are in contact and is opposite to the direction of any potential slipping. It’s drawn in the same direction as motion.
  • Air resistance: force drawn from the centre of mass opposing the direction of motion of the body.
34
Q

What is a balanced force?

A
  • When there are 2 or mroe forces acting on a body that are equal in size but opposite in direction.
  • The net force is 0 as there is no change in state of motion.
35
Q

What is an unbalanced force?

A
  • Created when a force acting in one direction in larger than the force acting in the oppostie direction.
  • Upward acceleration is caused when reaction force becomes greater than the weight force.
36
Q

What can be shown in vector diagrams?

A
  • The effects of internal and external forces can be represented as vector diagrams.
  • A high jumper will generate a large internal force from the muslces in the leg to create a big reacion force. This will help them to acheive vertical displacement + small horizontal force = high trajectory/closer to vertical
  • A long jumper will generate a large internal force from the muscles in the leg to create a horizontal force to generate a large horizontal distance + small vertical force = low trajectory/below 45’
37
Q

What is an impulse?

A
  • A force is always required to change a state of motion. Forces arent applied immediately. It takes time for a force to be applied. Impulse therefore, is the time taken for a force to be applied
  • Impulse = force x time
  • Measured as N.s
  • Newton’s 2nd law takes into account impulse linked tp momentum. If the impulse increases so does the rate if change of momentum = large change in velocity.
38
Q

How can an impulse increase speed?

A
  • Increase amount of internal muscular force applied
  • Decrease amount of time in which the force is applied.
39
Q

How can an impulse decrease speed?

A
  • Increase the time that a force acts on the body/object
40
Q

Force time graph: Start

A
  • Net impulse is a combination of positive and negative impulse.
  • Here the net impulse is positive which shows the performer to be accelerating
41
Q

Force time graph: Middle

A
  • Both positive and negative impulses are equal.
  • Net impulse is 0. There is no acceleration or deceleration. The performer is running at a constant velocity.
42
Q

Force time graph: End

A
  • The net impulse is negative whcih shows the sprinter to be decelerating

PE A-Level Mrs Rex (45 decks)

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