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.
2
Q
What is a scalar quantity?
A
- A quantity that has magnitude
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
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
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.
6
Q
What is distance?
A
- The path a body takes as it moves from the starting to finishing position.
- Measured in Metres (m)
7
Q
What is displacement?
A
- Shortest rate in a straight line between startig and finishing position.
8
Q
What is speed?
A
- The rate of change of a position
- Speed (m/s) = distance covered (m) / time taken (s)
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)
10
Q
Distance time graphs: Stationary
A
- Line doesnt go up or down.
- No distance travelled
- Performer is stationary
11
Q
DIstance time graphs: Constant speed
A
- Constant diagonal direction.
- Distance run is changing at a constant rate and at the same speed.
12
Q
Distance time graph: Acceleration
A
- Curve gets gradually steeper.
- More distance covered in a certain amount of time
13
Q
Distance time graph: Deceleration
A
- Curve levels off
- Less distance covered in a certain amount of time.
14
Q
Velocity time graph: Constant velocity
A
- Gradient remains constant, indicates performer is travelling a constant velocity.
15
Q
Velocity time graph: Acceleration
A
- Gradient gets steeper, indicates performer is moving with increasing velocity.
16
Q
Velocity time graph: Deceleration
A
- Gradient decreases, indicates performer is mocing with decreasing velocity.
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
