Biomechanics

Question 1

Define Linear motion

Answer 1

movement of a body in a straight or curved line and all parts move the same distance, in the same direction, in the same time

Question 2

Define Angular motion

Answer 2

movement of a body in a circular path about an axis of rotation

Question 3

EQ. Describe the factors, other than mass, that impact on the air resistance of a ball in flight. (4 marks)

Answer 3

• as velocity increases, AR does as well
• the more streamlined the shape is, the lower the AR
• the smaller the front cross sectional area, the lower the AR
• the smoother the surface, the lower the AR

Question 4

EQ. Define the term ‘angular velocity’. Give an equation for its calculation and state the units it is
measured in. (3 marks)

Answer 4

• angular velocity is the speed of rotation
• given by the change in angular displacement/ time
• rad/s

Question 5

Define displacement

Answer 5

shortest straight-line route from start to finish

Question 6

Define distance

Answer 6

total length of the path covered from start to finish

Question 7

Define speed and state formula used and units

Answer 7

rate of change in distance. distance/time. m/s

Question 8

Define velocity and state formula used and units

Answer 8

rate of change in displacement. displacement/time. m/s

Question 9

Define acceleration and state formula used and units

Answer 9

rate of change in velocity. velocity/time. m/s/s

Question 10

Define moment of inertia and the units its measured in.

Answer 10

the resistance of a body to change its state of angular motion or rotation. kgm²rad/s

Question 11

Define angular momentum and state formula used and units

Answer 11

the quantity of angular motion possessed by a body. moment of inertia x angular velocity. kgm²rad/s

Question 12

When angular velocity is high, moment of inertia is…

Answer 12

low

Question 13

What is the conservation of angular momentum

Answer 13

angular momentum is a conserved quantity which remains constant unless an external eccentric force or torque is applied

Question 14

What is the angular analogue of newtons first law of motion

Answer 14

a rotating body will continue to turn about its axis of rotation with constant angular momentum unless acted upon by an eccentric force

Question 15

EQ. Define momentum and calculate the sprinters momentum when they have a mass of 70kg and run at a velocity of 10m/s. (3 marks)

Answer 15

quantity of motion possessed by a moving body. 70x10=700kgm/s

Question 16

At what velocity must a 100kg athlete run to have a momentum of 900kgm/s

Answer 16

9m/s

Question 17

Define the term ‘centre of mass’.

Answer 17

the point at which the body is balanced

Question 18

EQ. Identify the vertical forces acting on a gymnast and explain their relationship during the handstand. (3 marks)

Answer 18

• weight and reaction are acting on the gymnast
• weight and reaction are equal to each other
• both forces are equal and act in opposite directions
• net force=0

Question 19

EQ. Define angular motion and explain how it is generated to produce a somersalt. (2 marks)

Answer 19

• angular motion is the movement of a body in a circular path about an axis of rotation
• generated when a force is applied outside the COM of a body

Question 20

EQ. Describe the factors that affect the size of moment of inertia of the trampolinist during the front somersalt. (2 marks)

Answer 20

• mass

- distance of mass from the axis of rotation

Question 21

EQ. Explain 3 factors that affect the horizontal distance travelled by a shot put. (3 marks)

Answer 21

• greater velocity increases distance
• angle of release should be less than 45*
• the greater the release height the further the distance

Question 22

EQ. Identify three factors that affect the stability of a gymnast (3 marks)

Answer 22

• height of centre of mass
• size of plane of support
• position of line of gravity

Question 23

EQ. One football travels in a straight line and another swerves during flight. Explain the effect of the application of force on the resulting motion of each football in flight. (4 marks)

Answer 23

• ball travelling in straight line has linear motion
• force is applied directly through the COM
• ball swerving has angula motion
• force is applied not throught the COM

Question 24

EQ. An ice skater spins about their longitudinal axis by generating angular momentum. Use the angular analogue of Newton’s 1st law of motion to explain how the skater can increase their rate of spin. (4 marks)

Answer 24

• a rotating body will continue to turn about its axis of rotation with constant angular momentum unless acted on by an extrenal force
• the skater should tuck their arms in
• to reduce moment of inertia and increase angular velocity
• AM=MI x AV