11.1: Linear Motion Flashcards
Scalar quantity definition:
- when measurements are only described in terms of size or magnitude.
Examples of scalar quantities:
- mass, distance and speed
Vector quantities definition:
- when measurements are described in terms of magnitude and directions.
Examples of vector quantities:
- weight, acceleration, displacement, velocity and momentum
What are vectors?
- usually represented by arrows. The length of the arrow shows the magnitude and the longer the arrow, the bigger the size.
- direction is shown by a line of application, a point of application and an arrow head.
Mass definition:
- the quantity of matter the body possesses.
Distance definition:
- measured in metered and is the path a body takes as it moves from the starting to the finishing position.
Displacement definition:
- measured in metres and is the shortest route in a straight line between the starting and finishing position.
Speed definition:
- a measurement in metres/second (m/s) of the body’s movement per unit of times with no reference in direction.
Velocity definition:
- measured in metres/second (m/s) and is the rate of change of displacement.
Why is weight a vector quantity?
- because it has both size and direction as it acts downwards from the centre of mass.
Why is mass a scalar quantity?
- because it does not have a direction, just size.
What is the weight equation?
- W = m x g (9.8)
What is the speed equation?
- speed = (m/s) = distance (m) / time (s)
What is the velocity equation?
- velocity = displacement (m) / time taken (s’
Speed vs velocity:
- speed and velocity are measurements of how fast a body moves.
- speed is a scalar quantity and is the rate of change of distance.
Diagram:
- A-B: constant speed
- B-C: deceleration
- C-D: no motion
What is acceleration?
- the rate of change of velocity.
- when velocity increases, positive acceleration occurs and when velocity decreases, negative acceleration takes place.
- measured in m/s (squared)
What is the acceleration equation?
- acceleration = the change in velocity / time
What is the change in velocity equation?
Final velocity - initial velocity / time
What is momentum?
- the product of the mass and velocity of an object
- vector quantity - has both magnitude and direction
- dependent upon mass and velocity , if one increases momentum increases
What is the momentum equation?
- momentum = mass (in kg) x v (in m/s)
External force definition:
- force from outside the body, e.g. the quadriceps contract concentrically to extend the knee in a jump.
Internal force definition:
- is generated by the skeletal muscles, e.g. friction, air resistance and weight.
Weight definition:
- the gravitational force exerted on an object.
- weight = mass -x acceleration, due to gravity and is measured in Newton’s (N)
Reaction force definition:
- this occurs when two bodies are in contact with one another.
Friction definition:
- occurs when two or more bodies are in contact with one another.
Air resistance definition:
- a force that acts in the opposite direction to the motion of a body travelling through the air.
What are the vertical forces?
- weight
- reaction force
What are horizontal forces?
- frictional force
- air resistance
- net force
What are the two types of frictional force?
- static
- sliding
Static definition:
- force exerted on one surface by another when there is no motion between the two surfaces.
- occurs before an object starts to slide.
- dry friction
Sliding definition:
- when dry friction acts between two surfaces that are moving relative to one another, sliding friction occurs.
What are the factors that can affect friction?
- the surface characteristics of the two bodies in contact
- the temperature of the bodies
- the mass of the objects that are sliding. The larger the mass results in greater friction.
What does air resistance depend on?
- the velocity of the moving body.
- the cross-sectional area of a moving body.
- the shape and surface characteristics of a moving body.
What is net force?
- resultant force acting on the body when all other forces have been considered.
- balanced vs unbalanced forces.
Balanced force definition:
- when there are two or more forces acting on a body that are equal in size but opposite in direction.
- when standing, the weight force and reaction force are equal in size but opposite in direction = zero net force.
Unbalanced force definition:
- when a force acting in one direction on a body is larger than a force acting in the opposite direction.
- when jumping the RF is bigger than the WF.
Impulse equation:
- impulse (m/s) = force x time.
Net impulse definition:
- a combination of positive and negative impulses.
