Flashcards in Chapter 4 - Biomechanical Movement (Paper 2) Deck (148):
What are scalar quantities?
Quantities that just have size.
what are vector quantities?
Quantities that have size and direction.
Name examples of scalar quantities?
Name examples of vector quantities?
How are vectors usually represented?
What is mass?
The quality of matter the body possesses.
What is weight?
The gravitational force exerted on an object.
If you measured how heavy a person is, what is that?
How do you calculate weight?
Mass (kg) x Gravity (9.8) = Weight (newtons)
If you calculate a persons weight on earth and on the moon, will it be the same?
No, because weight = mass (kg) x gravity and the gravity on the moon is different to that on earth and therefore the person will have a different weight.
What is distance?
Measured in metres and is the path a body takes as it moves from the starting to the finishing position.
What are distance and displacement used to describe?
They are used to describe the extent of a body's motion.
What is displacement?
Measured in metres and is the shortest route in a straight line between the starting and finishing position.
Why is distance a scalar quantity?
Because it just measures size.
Why is displacement a vector quantity?
Because it describes the direction as well as size.
What is speed?
A measurement in metres/second of the body's movement per unit of time with no reference to direction.
What is velocity?
Measured in metres/seconds and is the rate of changing displacement.
What do speed and velocity measure?
How fast a body moves.
How is speed a scalar quantity?
It is a scalar quantity since it does not consider direction.
How do you calculate speed?
Speed (m/s) = Distance covered (m) / Time taken (s)
Why is velocity a precise description of motion?
It explains how fast a body is moving and in what direction.
What is the calculation for velocity?
Displacement (m) / Time taken (s)
How to work out the gradient of a graph?
Changes in the y axis / Changes in the x axis
What is acceleration?
Measured in m/s2 and is the rate of change of velocity.
What happens to acceleration when velocity increases?
Positive acceleration occurs
What happens to acceleration when velocity decreases?
How do you calculate acceleration?
Change in velocity (m/s) / Time (s)
How do calculate change in velocity, which is needed to calculate acceleration?
Final velocity (Vf) - Initial velocity (Vi) / Time
What is momentum?
Momentum (kgm/s) = Mass (kg) x velocity (m/s)
Is momentum a scalar or vector quantity?
It is a vector quantity because momentum is calculate using velocity which has a magnitude and direction.
What happens to the momentum if the velocity or mass increases?
The momentum increases
How can momentum be conserved?
Momentum can be conserved when a performer or objet is in flight because neither mass or velocity can be changed. When throwing a ball, a fast arm action will allow the ball to travel at a greater velocity. But once in the air, this velocity cannot be changed unless an external force (such as gravity) acts upon it.
What is a external force?
Comes from outside the body.
What is an internal force?
Is generated by the skeletal muscles.
What does a force do to state of motion?
A force changes a body's state of motion.
Give examples of external forces.
How is weight calculate?
Mass x acceleration
What are the vertical forces that act upon a performer during linear motion?
What is a reaction force?
This occurs when two bodies are in contact with one another.
What is Newton's third law?
For every action force there is an equal and opposite reaction force.
What are the horizontal forces that act upon a performer during linear motion?
What are the two types of frictional force?
Static and sliding
What is static friction force?
It is the force exerted on one surface by another when there is no motion between two surfaces. In other words, static friction occurs before an object starts to slide.
Give an example of static friction.
The friction generated between the surface of a netball court and the sole of a shoe.
What is sliding friction?
It is when friction acts between two surfaces that are moving relative to one another. This is when there are two bodies in contact with one another that may have tendency to slip/slide over each other.
How can friction be affected?
-the surface characteristics of the two bodies in contact.
-the temperature of the two surfaces in contact (warmer temperatures have lower friction)
-the mass of the objects that are sliding (larger mass = greater friction)
What is friction?
Occurs when two or more bodies are in contact with one another.
What is air resistance?
A force that acts in the opposite direction to the motion of a body travelling through the air.
What does air resistance depend on?
-The velocity of the moving body - the faster the performer moves, the greater the air resistance.
-The cross-sectional area of the moving body. The larger the cross-sectional area, the greater the air resistance.
-The shape and the surface characteristics of a moving body. A streamlined shape results in less resistance, as does a smooth surface.
In water, what is air resistance referred to as?
On a diagram where do you draw the weight arrow?
The weight force is always drawn down from the centre of mass.
On a diagram where is the reaction arrow drawn?
The reaction force starts from where two bodies are in contact with one another. This contact can be the foot with the ground and is therefore drawn in an upward direction or can be the contact between sports equipment and a ball such as a tennis racket with a tennis ball.
On a diagram where is the friction arrow drawn?
The friction force starts from where the two bodies are in contact and is opposite to the direction of any potential slipping. It is the same direction as motion.
On a diagram where is the air resistance arrow drawn?
Air resistance is drawn from the centre of mass opposing the direction of motion of the body.
What does the length of the arrow drawn reflect?
It reflects the magnitude or size of the force: the longer the arrow, the bigger the size of the force.
What is net force?
This is the resultant force acting on a body when all other forces have been considered.
What is a balanced force?
A balanced force is when there are two or more forces acting on a body that are equal in size but opposite in direction.
Describe in terms of net force what happens when we are standing?
When standing, the weight force and reaction force are equal in size but opposite in direction. In this case, there is a zero net force, and therefore no change in the state of motion.
What is an unbalanced force?
An unbalanced force is when a force acting in one direction on a body is larger than a force acting in the opposite direction.
In terms of net force what happens when a person jumps.
It is an unbalanced force as the reaction force is bigger than the weight force allowing the performer to accelerate upwards.
How do you calculate impulse?
Impulse (newton seconds)= force x time
What is the calculation for momentum?
Momentum = Mass - Acceleration
An increase in an impulse will cause what?
An increase in impulse will result in an increase in the rate of change of momentum, which causes a large change in velocity.
What is an impulse?
The time it takes a force to be applied to an object or body.
What are the ways impulse can be used to increase momentum?
-Increasing the amount of muscular force that is applied.
-Increasing the amount of time in which a force is applied (to a body or object)
What are the ways impulse can be used to decrease the momentum?
By increasing the time forces act upon an object or body.
What is the net impulse?
A combination of both positive and negative impulses.
What is angular motion?
Movement around a fixed point.
Angular motion involves both ...
The whole body or part of a body such as arms
When does angular motion occur?
When force is applied outside the centre of mass.
What is an off centred force referred to as?
An eccentric force
When angular motion occurs the body can rotate in one of three axis. What are these axis?
Transverse - side to side across the body
-Sagittal - which runs from front to back
-Longitudinal - which runs from top to bottom
What is torque?
The rotational consequence of a force.
Why does angular motion occur?
Angular motion occurs as a result of torque (moment). A torque is a turning force. It causes an object to turn about its axis of rotation.
How can the torque be increased?
Applying the same force further away from the axis of rotation also increases the torque.
How do you calculate the moment of force or torque?
Force (newtons) x Perpendicular distance from the fulcrum (metres)
What is the momentum of force or torque measured in?
What is Newton's first law applied to angular motion?
A rotating body will continue to turn about its axis of rotation with constant angular motion unless an external rotational force (torque) is exerted upon it.
What is Newton's second law applied to angular motion?
The rate of change of angular momentum of a body is proportional to the force (torque) causing it and the change that takes place in the direction in which the force (torque) acts.
What is Newton's third law applied to angular motion?
When a force (torque) is applied by one body to another; the second body will exert an equal and opposite force (torque) on the other body.
What is radian?
The unit of measurement for angles.
Define angular displacement?
The smallest change in angle between the start and finish point of rotation.
Define angular velocity?
The rate of change of angular displacement.
Define angular acceleration?
The rate of change of angular velocity.
What is the formula for angular velocity?
Angular displacement (rad) / Time taken (s)
What are the units for angular velocity?
Describe angular velocity?
It refers to the rotational speed of an object and the axis about which the object is rotating.
What is the formula for angular acceleration?
Change in angular velocity (rad/s) / Time taken (s)
What is one radian in degrees?
What is inertia?
Resistance to a change in motion.
What is moment of inertia?
Is the resistance of a body to angular motion.
How can moment of inertia be applied to the start of rotation on a bar for example and how does this change?
At the start of of rotation when a body will resist angular motion; but once the rotation occurs, the body will want to turn about its axis of rotation.
What does moment of inertia depend on?
The mass of the body and the distribution of the mass around the axis.
How does the mass of a body or object affect the moment of inertia?
The greater the mass, the greater the resistance to change and therefore the greater the moment of inertia.
How does the distribution of mass from the axis of rotation affect the moment of inertia?
The closer the mass is to the axis of rotation, the easier it is to turn, because the moment of inertia is low. Increasing the distance of the distribution of mass from the axis of rotation will increase the moment of inertia.
What is angular momentum?
Is the quantity of rotation a body possesses (spin).
What is the formula for angular momentum?
Moment of inertia x angular velocity
What is the relationship between moment of inertia and angular velocity?
They are inversely proportional: if the moment of inertia increases, angular velocity decreases.
Angular momentum is described as being a conserved quantity. What does this mean?
It stays constant unless an external torque (force) acts upon it.
Describe how a figure skater is able to spin faster and slow down using moment of inertia.
At the start of the spin, the arms and legs are stretched out. This increases their distance from the axis of rotation, resulting in large moment of inertia and a large angular momentum in order to the start the spin, so rotation is slow. When the figure skater brings their arms and legs back in line with the rest of the body, the distance of these body parts to the action of rotation decreases significantly. This reduces the moment of inertia, which in turn increases their angular velocity and the skater spins very quickly.
What is projectile motion?
It refers to the movement of either an object or the human body as they travel through the air.
What is horizontal displacement?
The shortest distance from the starting point to the finishing point in a line parallel to the ground.
What are the factors affecting the horizontal displacement of a projectile?
-Angle of release
-Speed of release
-Height of release
How does the angle of release affect the horizontal displacement?
When both the release height and the landing height are equal, then the optimum angle of release is 45 degrees (ignoring wind resistance and gravity). If the release height is below the landing height, then the optimum angle needs to be greater than 45 degrees celsius. If the release height is greater than the landing height, the optimum angle of release needs to be less than 45 degrees celsius.
What is the optimum angle of release depend on?
Release height and landing height.
How does the speed of release affect the horizontal displacement?
The greater the release velocity of projectile, the greater the horizontal displacement travelled.
How does the height of release affect the horizontal displacement?
A greater release height also results in horizontal displacement.
What is a parabola?
A curve with the matching left and right hand side.
What are the factors that affect the flight paths of different projectiles?
What factors are crucial in deciding whether a projectile has a flight path that is a true parabola or a distorted parabola?
Weight (gravity) and air resistance
What type of projectiles follow a true parabolic flight path?
Projectiles with a large weight force have a small air resistance force and follow a true parabolic flight path.
When can air resistance have the greatest impact on projectile?
The longer the flight path the longer air resistance can affect a projectile and have a greater influence.
How does air resistance affect lighter objects?
The effects of air resistance result in a flight path that deviates from a true parabola to a distorted parabola.
What is the horizontal component?
The horizontal motion of an object.
What is the vertical component?
The upward motion of an object.
What are the vector components?
How can the vector components be drawn on a graph?
A vector is drawn as an arrow and it has a magnitude and direction.
What is the difference between the arrow drawn for the release point compared to the landing point?
The release point is higher than the landing point.
What stays the same regarding the vector component arrow at different parts of the flight?
The horizontal component arrow stays the same at each stage of the flight.
How do you get a resultant vector?
By adding the vertical and horizontal vector together.
What is fluid mechanics?
Fluid mechanics is the study of an object or the human body that travels through any liquid or gas.
Give an example of the human body relating to fluid mechanics.
Swimmers travel through the water.
What is fluid dynamics?
It is concerned with the movement of liquids and gases. It is a branch of fluid mechanics which is the study of fluids and how forces affect them.
What are the dynamic fluid forces?
What is a drag force?
A force that acts in opposition to motion.
What is drag caused by?
It is the resistance force caused by the motion of a body traveling through a fluid.
What is the affect of drag on velocity?
It has a negative affect, decreases velocity.
What is a drag force produced from?
Air resistance and friction.
What are the two types of drag?
What is surface drag?
It relates to friction between the surface of an object and the fluid environment.
What is surface drag also known as?
What is form drag?
It relates to the impact of the fluid environment on an object.
What is form drag also known as?
What does form drag relate to?
What are the factors that affect drag?
-Velocity of the moving body
-Cross-sectional area of the moving body
-The shape and the surface characteristics of a moving body
What is streamlining?
Involves shaping a body so it can move as effectively and quickly through a fluid as possible.
How does the velocity of the moving body affect drag?
The greater the velocity of a body through a fluid, the greater the drag force.
In sports that are very quick what is done to reduce the possible effects of drag?
Streamlining the body as much as possible.
How does the cross-sectional area affect drag?
The cross-sectional area of a moving body can reduce or increase drag. A large cross-sectional area increases drag.
How does the shape and surface affect the drag of a moving body?
A more streamlined, aerodynamic shape reduces drag. Sports scientists are regularly trailing drag-resistant clothing to achieve 'marginal gains' in speed to give competitors the edge over their opposition.
What is lift force?
Causes a body to move perpendicular to the direction of travel.
What is the Bernoulli principle?
Where air molecules exert less pressure the faster they travel and more pressure when they travel slower.
What is the angle of attack?
The tilt of a projectile relative to the flow of air.
The more lift force a projectile has during the .... it will stay in the air.
What does the angle of attack change?
The angle of attack changes the flow of air around an object so the air that travels over the top of the discus has to travel a longer distance than the air underneath.
What happens to the flight of a discus if the air above the discus is moving faster?
This creates a lower pressure. The lower pressure above the discus creates an upward lift force and allows the discus to stay in the air for longer, resulting in a greater horizontal distance.
What happens if the angle of attack is too great?
Then lift is reduced and drag increases, causing the discus to stall.