11.1 Linear Motion

Question 1

What is a scalar quantity?

Answer 1

• Quantities that just have size (magnitude)

Question 2

What is a vector quantity?

Answer 2

• Quantities that just have magnitude and direction

Question 3

What is mass?

Answer 3

The quality/amount of matter the body possesses

Mass is a scalar quanitity because it does not have direction, just size

Question 4

What is the calculation for weight?

Answer 4

Mass X Gravity= Weight

Question 5

What is distance?

Answer 5

• Measured in meters & is the path a body takes as it moves from the starting to the finish position

Distance & displacement are used to describe the extent of a bodys motion

Question 6

What is displacement?

Answer 6

Measured in meters & is the shortest route in a straight line between the starting & finishing position

Question 7

What is speed?

Answer 7

• How fast the body moves
  (With no reference to direction)

Question 8

What is the formula for speed?

Answer 8

Distance/Time

Question 9

What is velocity?

Answer 9

• Refers to how fast a body travels in a certain direction

Question 10

What is the formula for velocity?

Answer 10

Displacement/ Time taken

Question 11

What is acceleration?

Answer 11

• The rate of change of velocity
• When velocity increases positive acceleration occurs
• When velocity decreases, negative acceleration takes place

Question 12

How do you calculate acceleration?

Answer 12

Change in velocity/ Time

Question 13

How do you calculate the final change in velocity?

Answer 13

Final velocity- Initial velocity/Time

Question 14

What is momentum?

Answer 14

• The product of the mass and velocity of an object

Question 15

How do you calculate momentum?

Answer 15

Mass x Velocity

Question 16

What are the two vertical forces?

Answer 16

• Weight
• Reaction Force

Question 17

What is weight?

Answer 17

• The gravitational force exerted on an object.

Weight= mass x acceleration due to gravity & is measured in newtons (N)

Question 18

What is reaction force?

Answer 18

• Occurs when two bodies are in contact with one another

Question 19

What are the different types of horizontal forces?

Answer 19

• Frictional Force
• Air Resistance
• Net Force

Question 20

What are the two types of frictional force?

Answer 20

• Static: The force exerted on one surface by another when there is no motion between the two surfaces e.g. the surface of the netball court & the sole of a shoe
• Sliding: When there are two bodies in contact with one another that may have a tendancy to slip/slide over each other
  -Friction acts in opposition to motion.

Question 21

What factors can affect friction?

Answer 21

• The surface characteristics of the two bodies in contact e.g. a 100m sprinter who wears spikes, these help to increase friction & maximise acceleration
• The temperature of the two surfaces in contact.e.g. in curling ice is swept infront on curling stone- sweeping action slightly raises temp of ice which reduces the friction between stone & ice, allowing stone to travel further
• The mass of the objects that are sliding A larger mass results in greater friction

Question 22

What is air resistance?

Answer 22

• A force that acts in the opposite direction to the motion of a body travelling throught the air

Question 23

What does air resistance depend on?

Answer 23

• Velocity of moving body
• Cross sectional area of moving body- larger this is great AR
• Shape & Surface characteristics of a moving body- streamline shape results in less resistance

Question 24

What is net force?

Answer 24

• The resultant force acting on a body when all other forces have been considered.
• Often discussed in terms of balanced & unbalanced forces
• A balanced force: When there are 2 or more forces acting on a body that are equal in size but opposite in direction e.g. when standing weight force & reaction force are equal in size but opposite direction- so wld be zero net force & no change in state of motion
• An unbalanced force is when a force acting in one direction on a body is larger than a force acting in the opposite direction.
• E.G. when jumping in the air the performer accelerates upwards as the reaction force is bigger than the weight force

If friction arrow is longer than air resistance arrow, the body will accelerate & if it is shorter it will decellerate

Question 25

What is impulse?

Answer 25

- The time it takes a force to be applied to an object or body - An increase in impulse results in an increase in the rate of change of momentum which causes a large change in velocity - Impulse can be used to both speed up & slow down an object on impact ## Footnote Follows on from Newtons 1st law that a force is required to change a state of motion of a body- it will take a certain amount of time to apply this force.

Question 26

How is impulse calculated?

Answer 26

Impulse= Force X Time

Question 27

How do you use impulse to decrease momentum of an object?

Answer 27

- By increasing the time forces act upon them - e.g. in any activity that involves landing action such as gymnast dismounting from bars, flexion of the knee,hip & ankle occur,which extends the time of force on the ground (how long feet are in contact w mat) & therefore allows gymnast to control landing & also reduces chance of injury.

Question 28

How do you use impulse to increase momentum?

Answer 28

- By increasing amount of muscular force that is applied or by using impulse, to increase amount of time in which a force is applied. - e.g. in hammerthrow you often do 3-4 turns instead of a single swing.