biomechanics principles

Question 1

what is law of inertia (1st law)?

Answer 1

a body continues in a state of rest or uniform velocity unless acted upon by an external or unbalances force

Question 2

what is an practical example of law of inertia?

Answer 2

a gold ball will remains till unless the force applied by a gold club makes it move.

Question 3

what is law of acceleration (2nd law)?

Answer 3

a body’s rate of change of momentum is proportional t the size of the force applied and acts as the force applied

Question 4

what is a practical example of la of acceleration?

Answer 4

when a golf ball is struck by a golf club the rate of change of momentum of the ball is proportional to the size of the force acted upon it by the club. The bigger the force the greater the acceleration

Question 5

what is law of reaction (3rd law) ?

Answer 5

for every action there is an equal and opposite reaction

Question 6

what is a practical example of law of reaction?

Answer 6

if a tennis player hits a ball the racquet exerts a force on the ball and the ball exerts an equal and opposite force on the racquet

Question 7

what is velocity ?

Answer 7

rate of change of displacement

velocity=displacement/time taken

Question 8

what is momentum ?

Answer 8

quantity of motion possessed by a moving body

momentum=mass x velocity

Question 9

what is acceleration?

Answer 9

rate of change of velocity

acceleration=(final velocity-initial velocity)/time taken

Question 10

what is force?

Answer 10

a push or pull that alters the state of motion of a body

force= mass x acceleration

Question 11

vertical forces

Answer 11

weight and reaction

Question 12

horizaontal forces

Answer 12

friction and air resistance

Question 13

what is weight ?

Answer 13

is the gravitational pull that earth exerts on body

Question 14

what is reaction rate ?

Answer 14

is the equal and opposite force exerted by a body in response to the action force placed upon it

Question 15

what is friction ?

Answer 15

is the force that opposed the motion if two surfaces in contact

Question 16

what factors effect friction ?

Answer 16

1. roughness of the ground surface: e.g athletes run on rough, rubberised tracks
2. roughness of the contact surfaces: e.g athletes wear spiked shoes
3. temperature e.g F1 drivers have a warm up lap as friction is increased with higher tyre temperatures
4. size of normal reaction: snot putters have a high mass due to newtons third law this creates an equal and opposite high reaction force allowing greater friction in the throwing circle and preventing over rotation.

Question 17

what is air resistance ?

Answer 17

is the force that opposed motion through the air.

Question 18

what are the factors that affect air resistance ?

Answer 18

1. velocity: e.g the greater the velocity of a cyclist the greater the force of air resistance opposing their motion
2. shape: e.g most cyclist wear a tear drop shape helmet to minimise air resistance known as stream lining
3. frontal cross sectional area: e.g the low crouched position of a downhill skier reduces air resistance
4. smoothness of surface e.g increases smooth e.g lycra suits reduces air resistance

Question 19

free body diagrams vertical forces

Answer 19

1. if weight is equal to in size to reaction W=R net force is zero. The forces are balanced therefore the body will remain at rest e.g a basketball player preparing to take a free throw.
2. if reaction force is greater the weight R–>W then the net force is positive and forces are unbalanced and acceleration is an upward direction will occur e.g a basketball player leaving the ground in the take off phase pf a lay up shot

Question 20

free body diagrams horizontal forces

Answer 20

1. if friction is equal to air resistance net force is zero forces are balanced therefore the body will continue to travel at constant velocity e.g a sprint cyclist who has reached maximum velocity on the track
2. if friction is greater than air resistance net force is positive and forces are unbalanced and acceleration in a forward direction will occur e.g sprint cyclist accelerating away from the starting line
3. if air resistance is greater than friction net force is negative forces are unbalanced and horizontal deceleration occur e.g sprint cyclist crossing the finish line sitting up and decelerating

Question 21

what is centre of mass?

Answer 21

is the point which an object or a body is balanced in all directions

Question 22

what are the factors that effect stability?

Answer 22

1. mass of the body : the greater the mass the greater the inertia e.g sumo wrestler
2. height of the centre of mass: the lower the centre of mass the greater the stability
3. size of the base of support: the greater the size of base of support the greater the stability this can be increased by more points of contact
4. line of gravity: the more central the line of gravity to the base of support the greater the stability