11.1: Linear Motion

Question 1

Scalar quantity definition:

Answer 1

• when measurements are only described in terms of size or magnitude.

Question 2

Examples of scalar quantities:

Answer 2

• mass, distance and speed

Question 3

Vector quantities definition:

Answer 3

• when measurements are described in terms of magnitude and directions.

Question 4

Examples of vector quantities:

Answer 4

• weight, acceleration, displacement, velocity and momentum

Question 5

What are vectors?

Answer 5

• usually represented by arrows. The length of the arrow shows the magnitude and the longer the arrow, the bigger the size.
• direction is shown by a line of application, a point of application and an arrow head.

Question 6

Mass definition:

Answer 6

• the quantity of matter the body possesses.

Question 7

Distance definition:

Answer 7

• measured in metered and is the path a body takes as it moves from the starting to the finishing position.

Question 8

Displacement definition:

Answer 8

• measured in metres and is the shortest route in a straight line between the starting and finishing position.

Question 9

Speed definition:

Answer 9

• a measurement in metres/second (m/s) of the body’s movement per unit of times with no reference in direction.

Question 10

Velocity definition:

Answer 10

• measured in metres/second (m/s) and is the rate of change of displacement.

Question 11

Why is weight a vector quantity?

Answer 11

• because it has both size and direction as it acts downwards from the centre of mass.

Question 12

Why is mass a scalar quantity?

Answer 12

• because it does not have a direction, just size.

Question 13

What is the weight equation?

Answer 13

• W = m x g (9.8)

Question 14

What is the speed equation?

Answer 14

• speed = (m/s) = distance (m) / time (s)

Question 15

What is the velocity equation?

Answer 15

• velocity = displacement (m) / time taken (s’

Question 16

Speed vs velocity:

Answer 16

• speed and velocity are measurements of how fast a body moves.
• speed is a scalar quantity and is the rate of change of distance.

Question 17

Diagram:

Answer 17

• A-B: constant speed
• B-C: deceleration
• C-D: no motion

Question 18

What is acceleration?

Answer 18

• the rate of change of velocity.
• when velocity increases, positive acceleration occurs and when velocity decreases, negative acceleration takes place.
• measured in m/s (squared)

Question 19

What is the acceleration equation?

Answer 19

• acceleration = the change in velocity / time

Question 20

What is the change in velocity equation?

Answer 20

Final velocity - initial velocity / time

Question 21

What is momentum?

Answer 21

• the product of the mass and velocity of an object
• vector quantity - has both magnitude and direction
• dependent upon mass and velocity , if one increases momentum increases

Question 22

What is the momentum equation?

Answer 22

• momentum = mass (in kg) x v (in m/s)

Question 23

External force definition:

Answer 23

• force from outside the body, e.g. the quadriceps contract concentrically to extend the knee in a jump.

Question 24

Internal force definition:

Answer 24

• is generated by the skeletal muscles, e.g. friction, air resistance and weight.

Question 25

Weight definition:

Answer 25

• the gravitational force exerted on an object.
• weight = mass -x acceleration, due to gravity and is measured in Newton’s (N)

Question 26

Reaction force definition:

Answer 26

• this occurs when two bodies are in contact with one another.

Question 27

Friction definition:

Answer 27

• occurs when two or more bodies are in contact with one another.

Question 28

Air resistance definition:

Answer 28

• a force that acts in the opposite direction to the motion of a body travelling through the air.

Question 29

What are the vertical forces?

Answer 29

• weight
• reaction force

Question 30

What are horizontal forces?

Answer 30

• frictional force
• air resistance
• net force

Question 31

What are the two types of frictional force?

Answer 31

• static
• sliding

Question 32

Static definition:

Answer 32

• force exerted on one surface by another when there is no motion between the two surfaces.
• occurs before an object starts to slide.
• dry friction

Question 33

Sliding definition:

Answer 33

• when dry friction acts between two surfaces that are moving relative to one another, sliding friction occurs.

Question 34

What are the factors that can affect friction?

Answer 34

• the surface characteristics of the two bodies in contact
• the temperature of the bodies
• the mass of the objects that are sliding. The larger the mass results in greater friction.

Question 35

What does air resistance depend on?

Answer 35

• the velocity of the moving body.
• the cross-sectional area of a moving body.
• the shape and surface characteristics of a moving body.

Question 36

What is net force?

Answer 36

• resultant force acting on the body when all other forces have been considered.
• balanced vs unbalanced forces.

Question 37

Balanced force definition:

Answer 37

• when there are two or more forces acting on a body that are equal in size but opposite in direction.
• when standing, the weight force and reaction force are equal in size but opposite in direction = zero net force.

Question 38

Unbalanced force definition:

Answer 38

• when a force acting in one direction on a body is larger than a force acting in the opposite direction.
• when jumping the RF is bigger than the WF.

Question 39

Impulse equation:

Answer 39

• impulse (m/s) = force x time.

Question 40

Net impulse definition:

Answer 40

• a combination of positive and negative impulses.