Chapter 4 - Biomechanical Movement (Paper 2) Flashcards
What are scalar quantities?
Quantities that just have size.
what are vector quantities?
Quantities that have size and direction.
Name examples of scalar quantities?
- mass
- distance
- speed
Name examples of vector quantities?
- Weight
- Acceleration
- Displacement
- Velocity
- Momentum
How are vectors usually represented?
By arrows
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?
Their mass
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?
Negative acceleration
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.
- Friction
- Air resistance
- Weight
How is weight calculate?
Mass x acceleration
What are the vertical forces that act upon a performer during linear motion?
- Weight
- Reaction force
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?
- frictional force
- air resistance
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?
Drag
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.