Biomechanics Ultimate Exam: Quiz!

1.

Which plane of motion is labelled as number 1 in the diagram?

The transverse plane.

The sagital plane.

The frontal plane.

The plane of motion labelled as number 1 in the diagram is the frontal plane. The frontal plane separates the body vertically into front and back portions.

Explanation

The plane of motion labelled as number 1 in the diagram is the frontal plane. The frontal plane separates the body vertically into front and back portions.

2. Which plane of motion lies vertically and divides the body into left and right halves?

The frontal plane.

The transverse plane.

Anatomical neutral position.

The sagital plane.

The sagital plane lies vertically and divides the body into right and left parts.

Explanation

The sagital plane lies vertically and divides the body into right and left parts.

3. Which of these is not one of Newton's 3 laws of motion?

A body will continue in a state of rest of uniform velocity unless acted upon by an external force.

For every action there is an equal and opposite reaction.

A body moves in a circle about a point called the axis of rotation.

A body moves in a circle about a point called the axis of rotation is not one of Newton’s 3 laws of motion.

Explanation

A body moves in a circle about a point called the axis of rotation is not one of Newton’s 3 laws of motion.

4. What is velocity?

Velocity = change in displacement / time

Velocity = total distance travelled / time

Velocity = change in displacement / speed

Velocity = time / change in displacement

Velocity is equal to the change in displacement divided by time.

Explanation

Velocity is equal to the change in displacement divided by time.

5. What is the difference between distance and displacement?

Displacement is the distance between the start and end point only, distance is the total distance travelled along the path of motion

Explanation

Displacement is the distance between the start and end point only, distance is the total distance travelled along the path of motion

6. What is the magnitude of momentum of a cricket ball of mass 420g thrown at 20ms^-1?

8.1Ns

8.7Ns

8.4Ns

7.9Ns

Momentum = mv so 0.42x20=8.4Ns.

Explanation

Momentum = mv so 0.42x20=8.4Ns.

7. Which formula represents potential energy?

PE=mgh

PE=1/2mv2

PE=mh

PE=mgh2

PE=mgh. When a body is higher vertically it has a higher potential energy. There is no zero of potential energy.

Explanation

PE=mgh. When a body is higher vertically it has a higher potential energy. There is no zero of potential energy.

8. What is the definition of Kinetics?

The rate of change of displacement with respect to time.

Kinetics is the branch of mechanics that is concerned with the effects of forces on the motion of a body or system of bodies, especially of forces that do not originate within the system itself.

Explanation

Kinetics is the branch of mechanics that is concerned with the effects of forces on the motion of a body or system of bodies, especially of forces that do not originate within the system itself.

9. Rearrange the formula v=u+at to make t the subject

T=v-u/a

T=u+a/v

T=v-u/at

T=u+av

t=v-u/a is v=u+at rearranged to make t the subject. You would arrive at this answer by first subtracting u from both sides to give you v-u=at, then divide both sides by a to give you t=v-u/a

Explanation

t=v-u/a is v=u+at rearranged to make t the subject. You would arrive at this answer by first subtracting u from both sides to give you v-u=at, then divide both sides by a to give you t=v-u/a

10. A 5kg block is lifted from the floor onto a table 2 metre high. What is the work done?

98 Joules

115 Joules

90 Joules

102 Joules

98 Joules is the work done. This is calculated as Work done = Force x distance. F= 5x9.8=49N. 49x2=98J.

Explanation

98 Joules is the work done. This is calculated as Work done = Force x distance. F= 5x9.8=49N. 49x2=98J.

11. Which of the following statements best defines buoyancy?

An object will float if it is lighter than the fluid it is immersed in.

When surface tension is in equilibrium with the downward force applied by the immersed object.

Buoyancy can be defined as “A fluid will exert an upward force on an object immersed in it equal to the weight of the fluid displaced by the object.”

Explanation

Buoyancy can be defined as “A fluid will exert an upward force on an object immersed in it equal to the weight of the fluid displaced by the object.”

12. A high diver of mass 69kg leaps from a ledge 20m above the water. What is his potential energy at 10m above the water?

6805J

6030J

6502J

6762J

His potential energy will be 6762J. PE=mgh so 6762=69x9.8x10.

Explanation

His potential energy will be 6762J. PE=mgh so 6762=69x9.8x10.

13. What is the normal reaction force of an athlete weighing 45kg on a level surface?

430N

441N

470N

450N

This is calculated as 45x9.8=441N

Explanation

This is calculated as 45x9.8=441N

14. A squash player starts with her arm out straight in the frontal plane and swings her racquet back through 40^oto serve. What is this angle in radians?

0.698rad

0.712rad

0.691rad

0.687rad

40/360 x 2π = 0.698rad

Explanation

40/360 x 2π = 0.698rad

15. If a weight lifter has done 210.7J of work lifting a 50kg weight 0.43m from his shoulder in 0.7s, what was his power?

289W

301W

325W

310W

Power=work done/time taken so Power = 210.7/0.7=301W

Explanation

Power=work done/time taken so Power = 210.7/0.7=301W

16. Whats is the definiton of Kinematics?

If the forces acting upon an object are balanced, then the acceleration of that object will be 0 m/s/s.

Kinematics is the branch of mechanics that studies the motion of a body or a system of bodies without consideration given to its mass or the forces acting on it.

Explanation

Kinematics is the branch of mechanics that studies the motion of a body or a system of bodies without consideration given to its mass or the forces acting on it.

17. Why will a dimpled golf ball travel further than a smooth golf ball?

The dimpled golf ball creates a smaller area of turbulent air behind it which creates a smaller area of low pressure so there will be less drag. This is due to the boundary layer staying on the dimpled golf ball longer before peeling off so there will be a smaller area of low pressure.

Explanation

The dimpled golf ball creates a smaller area of turbulent air behind it which creates a smaller area of low pressure so there will be less drag. This is due to the boundary layer staying on the dimpled golf ball longer before peeling off so there will be a smaller area of low pressure.

18. What is Bernoulli's principle?

“As the velocity of a fluid increases, the pressure exerted by that fluid decreases.”

“As the velocity of a fluid decreases, the pressure exerted by that fluid decreases.”

“As the velocity of a fluid increases, the pressure exerted by that fluid increases.”

Bernoulli’s principle describes the relationship between the velocity of a moving liquid and the pressure exerted by the moving liquid, and that relationship is that as the velocity of the fluid increases, the pressure exerted by the fluid decreases.

Explanation

Bernoulli’s principle describes the relationship between the velocity of a moving liquid and the pressure exerted by the moving liquid, and that relationship is that as the velocity of the fluid increases, the pressure exerted by the fluid decreases.

19. In conservation of angular momentum what happens if the moment of inertia of an ice skater spinning becomes higher (assuming no angular momentum is lost?

The ice skater will spin faster

The ice skater will have lost angular momentum

The ice skater will spin slower

The ice skater will gain angular momentum

The ice skater will spin slower when the moment of inertia is increase, and they will spin faster when the moment of inertia is decreased.

Explanation

The ice skater will spin slower when the moment of inertia is increase, and they will spin faster when the moment of inertia is decreased.

20. If a pendulum swings from its starting position, 55° to left of vertical, to 30° right of vertical, then back to 9° left of vertical, then comes to rest in the vertical position, what is the angular displacement of the pendulum?

85º

46º

55º

133º

55º is the angular displacement of the pendulum. Angular displacement is the difference between the start and final position.

Explanation

55º is the angular displacement of the pendulum. Angular displacement is the difference between the start and final position.

21. How would you convert an angle in degrees to radians?

(angle in degrees)/360º x 2π = angle in radians

(angle in degrees)/2π x 360º = angle in radians

2π/360º x (angle in degrees) = angle in radians

(angle in degrees) x 360º / 2π = angle in radians

(angle in degrees)/360º x 2π = angle in radians

Explanation

(angle in degrees)/360º x 2π = angle in radians

22. A golf ball is chipped out of a bunker with an initial velocity of 9.3ms^-1 onto the green at an angle of 54° to the horizontal. The total flight time is 1.193s. What was the range of the ball?

6.52m

7.54m

6.01m

6.75m

The ball travelled 6.52m. This is calculated by shorz = Vhorz´T. Vhorz = 9.3cos54°=5.466ms-1.

Explanation

The ball travelled 6.52m. This is calculated by shorz = Vhorz´T. Vhorz = 9.3cos54°=5.466ms-1.

23. An aeroplane's wing is specially shaped so that it gets some of its lift due to Bernoulli's principle. Why is this?

An aeroplane’s wing is shaped so that more air travels over the wing than below it which creates higher pressure below the wing than above it so lift is created.

Explanation

An aeroplane’s wing is shaped so that more air travels over the wing than below it which creates higher pressure below the wing than above it so lift is created.

24. A golf ball is hit at an angle of elevation of 37° and an initial velocity of 45ms^-1. If all fluid forces are ignored and g is taken to 9. 8ms^-2 then what would the time to maximum height be?

4.78s

4.59s

5.82s

4.48s

The time to maximum height would be 4.59s. This is calculated using the equation t=v-u/a and substituting in the known values from the question.

Explanation

The time to maximum height would be 4.59s. This is calculated using the equation t=v-u/a and substituting in the known values from the question.

25. Which equation represents the coefficient of restitution?

-e = mg/u

-e = v/u

-e= mg(v/u)

-e = v x u

-e = v/u because the coefficient of restitution is the ratio of velocity of the ball after impact to the velocity of the ball before impact.

Explanation

-e = v/u because the coefficient of restitution is the ratio of velocity of the ball after impact to the velocity of the ball before impact.

26. If a golf ball is hit with an initial velocity of 41ms^-2 and it takes 4.184s to reach maximum height, what would the maximum height be? Take gravity to be 9. 8ms^-2

90.57m

82.34m

85.77m

87.29m

The maximum height would be 85.77m. This is calculated using the formula s=1/2(u+v)t and substituting the known values from the question.

Explanation

The maximum height would be 85.77m. This is calculated using the formula s=1/2(u+v)t and substituting the known values from the question.

27. An ice skater performs a spin. If his angular velocity is 4.3π rad.s^-1 and his moment of inertia is 0.9 kgm² at the beginning of the spin, what would his angular velocity be if his moment of inertia became 0.75kgm²? Assume that no angular momentum is lost.

17.19 πrad.s-1

16.21 πrad.s-1

16.75 πrad.s-1

16.52 πrad.s-1

0.9*4.3π=12.16 so 12.16/0.75=16.21πrad.s-1.

Explanation

0.9*4.3π=12.16 so 12.16/0.75=16.21πrad.s-1.

28. A block with a mass of 48kg is resting on a slope of a 23° angle. What is the normal reaction force of the block?

433N

470.4N

450N

480N

The normal reaction force of the block is 433N. This is calculated by first working out the weight of the block (48 x 9.8) and then multiplying by cos23 to find the normal reaction force relative to the angle the block is on.

Explanation

The normal reaction force of the block is 433N. This is calculated by first working out the weight of the block (48 x 9.8) and then multiplying by cos23 to find the normal reaction force relative to the angle the block is on.

29. A rugby prop sprints away from a scrum with an acceleration of 0.2ms^-2 for 10s. How far did he travel?

15m

20m

18m

10m

The prop ran 10m. This is worked out using the equation s=1/2(u+v)t. His final velocity will be 0.2ms-2 x 10s = 2ms-2 so S=1/2(0+2)10 so S=10m.

Explanation

The prop ran 10m. This is worked out using the equation s=1/2(u+v)t. His final velocity will be 0.2ms-2 x 10s = 2ms-2 so S=1/2(0+2)10 so S=10m.

30. What are the two main factors that affect the range of a projectile (when ignoring air resistance)?

Horizontal projection velocity and time of flight

Vertical projection velocity and time of flight

Angle of release and time of flight

Horizontal projection velocity and angle of release

Horizontal projection velocity and time of flight are the main factors affecting the range of a projectile. In the equation R=VcosƟ x tmax the angle of release is used to calculate the velocity in the horizontal direction.

Explanation

Horizontal projection velocity and time of flight are the main factors affecting the range of a projectile. In the equation R=VcosƟ x tmax the angle of release is used to calculate the velocity in the horizontal direction.