1.3 Flashcards
define angular distance
angle through which a body has rotated in moving from first position to the second
define angular displacement
shortest change in angular position/smallest angle through which a body can rotate to reach the second position from the first
value for angular distance when gymnast does double somersault
720*
value for angular displacement when gymnast does double somersault
0*
define centre of mass (2)
position in body which it is balanced in all directions; point at which the mass of a body is said to be concentrated/said to act
describe how performer applies eccentric force to ball (2)
is an off centre force; force applied outside the centre of mass of the ball
effect of an eccentric force on a ball (2)
create spin/angular motion/rotation; causes swerve/lift/deviation in flight
define the analogue of newtons first law of motion
a body will rotate with constant angular momentum unless acted upon by an external angular force
how a figure skater controls angular velocity while performing multiple spin about longitudinal axis (7)
AM=AV x MI; AM generated at start when off centre force applied to skater by the ice; start low AV; during arms/legs brought in to reduce MI; increases AV; at end arms/legs out to increase MI; reduce AV to prevent over rotation
define linear motion
movement in a straight line
explain how linear motion is created
direct force / force applied through centre of mass
velocity equation
velocity = distance / time
acceleration equation
acceleration = change in velocity / time
explain the concept of conservation of angular momentum using the angular analogue of newtons first law of motion (7)
a body will continue to rotate with constant AM; unless acted upon by eccentric force; AM = MI x AV; once in flight any change in MI will cause a change in AV to conserve AM; eg if diver tucks MI reduced so AV increases (means AM conserved during flight); performer can manipulate body shape to change MI and AV as AM remains constant
define angular motion (2)
movement of a body (in a circular path) about an axis of rotation; rotation of a body around an axis
explain how angular motion is generated to produce a somersault (2)
force applied outside CoM/axis of rotation; eccentric force
describe linear motion
movement of a body in a straight line and all parts move the same distance, in the same direction, in the same time
describe angular motion
movement of a body in a circular path about an axis of rotation
identify vertical forces acting on gymnast in a handstand and explain their relationship during the handstand (3)
weight and reaction force; W = R; forces are equal in size and opposite in direction/net force = 0/ forces are balanced
define angular velocity (2)
rate of change in angular displacement; speed of rotation
units of angular velocity
radians per second
why a gymnast in a bridge is more stable than a handstand (5)
more points of contact with the floor; larger base of support; lower centre of mass; line of gravity at centre of/falls further within the base of support; line of gravity easier to keep in centre of base of support
describe angular motion (2)
movement around an axis; generated by an eccentric force
example of angular motion
gymnast swings on or around the bar
use newtons laws of motion to explain how a sprinter can maximise performance during a sprint start (3)
1 - sprinter will remain stationary unless an unbalanced force acts on him; 2 - greater net/resultant/forward force on the sprinter the greater the sprinters acceleration; 3- sprinter applies force back and down into floor so ground applies equal up and forward force on sprinter
describe what is meant by inertia of a moving object (6)
inertia is resistance of a body to change its state of motion; depends on mass (bigger mass greater inertia); resistance to accelerate; resistance to decelerate/stop; resistance to change direction; larger inertia, greater force required to change its state of motion