Introduction to Force and Newton's Laws

Question 1

state what it is meant by the key term - biomechanics

Answer 1

biomechanics is the study of the structure and function of biological systems by means of the methods of mechanics

Question 2

state what it is meant by the key term - force (static)

Answer 2

the push or pull on an object resulting from the object’s interaction with another object

Question 3

state what it is meant by the key term - force (dynamic or internal)

Answer 3

the influence that causes a mass to be accelerated

Question 4

state 2 things you need to remember about force

Answer 4

1. a force is a vector quantity (magnitude, direction and sense)
2. it is measured in Newton’s (N) = 1kg m/s²

Question 5

state what it is meant by the key term - Newton’s 1st Law of Inertia

Answer 5

a body will remain in a position of rest, or constant velocity, unless acted upon by an external force causing it to change motion

Question 6

state what it is meant by the key term - inertia

Answer 6

inertia is the resistance of an object to change motion

Question 7

state what it is meant by the key term - Newton’s 2nd Law of Acceleration

Answer 7

the change in motion of an object is directly proportional to the force impressed and that change takes place in the direction of the straight line in which the force acts

Question 8

what are the equations for: A) force, and B) acceleration

Answer 8

A) f = m.a

B) a = (f x θ) / m

Question 9

state what it is meant by the key term - Newton’s 3rd Law of Action-Reaction

Answer 9

for every force there is an equal and opposite reaction. all reaction forces are equal in size and opposite in direction to all action forces

Question 10

how does anything move at all ?

Answer 10

the mass of the earth is used to out advantage

Question 11

state what it is meant by the key term - gravity

Answer 11

gravity is a non-contact force generated by the gravitational field and causes an object to accelerate on the earth at a rate of about g = -9.81 m/s²

Question 12

if we are concerned with vertical motion, and the forces determining that motion, what 4 things do we need to consider ?

Answer 12

1. we have-to consider the weight force (Fw) when calculating net vertical force
2. to calculate the resulting vertical acceleration, we must calculate the net vertical force
3. depending on the direction of movement, Fw may be supporting or opposing the intended motion
4. the total and net vertical forces may not be equal

Question 13

state what it is meant by the key term - Ground Reaction Force (GRF)

Answer 13

GRF is the reaction force provided by the surface upon which one is moving

Question 14

state 2 explanatory facts about GRF

Answer 14

1. a person pushes down with an application force (acts on the ground)
2. the ground pushes back with a force both equal and opposite (reacts on the person)

Question 15

what 2 things it is essential to remember when talking about GRF ?

Answer 15

1. GRF magnitude and direction affects the whole bodies COM motion
2. GRF is a vector and can be resolved in to it’s 3D components

Question 16

what is the piece of equipment usually used to measure GRF ?

Answer 16

a force plate/platform

Question 17

how does a force platform/plate work ? (2 points)

Answer 17

1. it senses the deformation produced by the applied force (electrical charge) which is proportional to the force
2. it is a very accurate tool, with sampling frequencies that may vary (e.g. - 50Hz for balance, 2000Hz for impacts)

Question 18

state 4 facts about load cells in relation to force plates

Answer 18

1. 4 load cells measure GRF in 3D
2. Ant/Post (x)
3. Med/Lat (y)
4. Vert (z)

Question 19

how do you convert from degrees to radians ?

Answer 19

degrees x (pi/180)