A2 PE Mechanics of Movement Flashcards
What is a scalar?
A quantity which only has a magnitude (size)
Speed, distance and mass are scalar quantities.
Linear motion is…
Movement of a body in a straight line where all parts are moving in the same direction at the same speed.
What is a vector?
A quantity that has both a direction and a magnitude (size).
Velocity, acceleration, momentum are all vectors.
It is demonstrated by an arrow which points in the direction of travel and is a length that represents the size of the force.
Speed =
Distance/time
Units are ms
Velocity =
Displacement / time (units are ms)
The amount of ground covered during motion is …
Distance (units are m)
How would you calculate displacement?
Straight line length from starting point to finishing point. (Units are m)
Acceleration =
Change in velocity/time
Vf-Vi/ time
(Units are ms)
Force =
Mass x acceleration.
E.g Weight = mass x gravity
Momentum =
Mass x velocity (units are kgms)
Impulse =
Force x time (units are ft)
When an athlete is RUNNING, the curve you would draw on an impulse graph always starts below the line, true or false?
True - this is the negative force applied when the sprinter lands on the track.
When a performer is leaving the blocks the force is totally above the line - they haven’t landed on the track yet.
When drawing an impulse graph for a sprinter who is moving at constant velocity, what would the graph look like?
A symmetrical ‘S’ shape where the negative force below the x axis is the same size and shape as the positive force above the x axis.
Name Newton’s first law, explain it and give and example.
INERTIA
A body continues in a state of rest or constant velocity unless acted upon by an external force.
E.g a swimmer will stay on the blocks until they contract their muscles to apply a force.
Name Newton’s second law, describe it and give an example.
ACCELERATION (force = mass x acceleration)
When a force acts on an object, the rate of change of velocity experienced by the object is proportional to the size of the force and travels in the direction the force is applied.
E.g the force used by a sprinter pushing off the starting blocks is equal to the force they will accelerate with in the opposite direction
Name Newton’s third law, describe it and give an example.
ACTION AND REACTION
For every action there is an equal and opposite reaction (ground reaction force)
E.g if a high jumper applies a force into the ground they will receive and equal and opposite force to allow them to jump into the air.
Forces are any push or pull which cause a change in velocity, what four things can forces do?
- Cause a body to move
- Cause a body to accelerate and decelerate
- Cause a body to change direction
- Cause a body to change shape
Give 3 examples of horizontal forces
Friction
Air resistance
Drag
Give three examples of vertical forces.
Gravity (9.8ms)
Weight force (mass x gravity)
Ground reaction force (from Newton’s 3rd law)
What is the name of the trajectory of an object in flight?
Parabola
What vertical force acts on a projectile while it is in the air?
Gravity
Which component of a parabola does gravity affect?
The vertical component - it causes the object to accelerate downwards when it is in flight. This causes the symmetrical ‘inverted U’ shape of the parabola.
What effect does air resistance have on a projectile like a person doing the long jump?
Very little as the mass of the performer is large.
It would affect the horizontal component, but it’s effect is considered to be ‘negligible’.
Give 3 factors that affect horizontal displacement of a projectile (how far the projectile travels)
Height of release
Velocity / speed of release
Angle of release
