Forces

Question 1

Torque and formula

Answer 1

Turning effect produced by force

Causes rotation around a central axis or fixed point

Formula: force x length of lever arm

Question 2

Effect of torque on angular acceleration

Answer 2

Torque causes rotation on an axis, therefore causes angular acceleration.
The greater the torque, the greater the angular acceleration.

Question 3

Eccentric force

Answer 3

Force that causes an object to turn or rotate but does not act through the object’s centre of gravity

Question 4

How is rotation and eccentric force used in sports

Answer 4

Eccentric force is used in sports such as racquet sports (tennis or cricket) to apply a ‘spin’ to the ball

Question 5

Angular velocity and units

Answer 5

Rate of change of angular displacement
Meadsured in degrees per second

Question 6

Angular displacement

Answer 6

Change in absolute angular position over time

Question 7

Factors that influence size of torque

Answer 7

Size of applied force and length of lever arm

Question 8

Relationship between angular and linear velocity

Answer 8

Linear velocity = angular velocity x radius of rotation
The rotational movement of swinging your leg to kick or racquet to hit causes linear movement of the ball.
To increase the linear velocity and distance travelled by the ball: increase angular velocity or length of implement (eg: cricket bat)

Question 9

Momentum and formula

Answer 9

The amount of motion an object has and its resistance to changing that motion.

Momentum (p) = mass (m) x velocity (v)

Question 10

Momentum and formula

Answer 10

The amount of motion an object has and its resistance to changing that motion

Momentum (p) = mass (m) x (velocity)

Question 11

Conservation of Momentum

Answer 11

The principle of conservation of momentum states that the total momentum of a system before a collision is equal to the total momentum of the system after the collision.

If they stay in touch, objects with move in the direction of the object with a higher momentum (eg: tackling in football)
If it’s only a hit, the smaller momentum object will move in the direction of the applied force (softball bat hitting ball)

Question 12

Explain conservation of momentum using a softball bat and ball example

Answer 12

Bat has a greater mass but lower velocity, ball has a lower mass but higher velocity therefore momentum remains the same until external forces act upon the ball like gravity.

Question 13

Force summation

Answer 13

Also known as summation of momentum.
The correct timing and sequencing of body parts to produce the maximum velocity.

Question 14

Points to mention for force summation

Answer 14

1. Larger, more powerful muscle groups (closer to the centre of gravity) generate the initial momentum which is then transferred to sequential muscles further away (limbs, hands, feet).
2. Stablise each body part after moving to ensure smooth and efficient movement, allows maximum transfer of momentum for a higher velocity.
3. Follow through with movements to avoid deceleration.

Question 15

Angular Velocity

Answer 15

The total rate of change of angular displacement
Measured in degrees per second

Question 16

Angular displacement

Answer 16

Total change in absolute angular position

Question 17

Angular momentum and formula

Answer 17

The amount of angular motion a rotating object has
Angular momentum = angular velocity x moment of inertia

Question 18

Moment of inertia and formula

Answer 18

A rotating objects resistance to changes in angular motion.
A rotating object will remain rotating unless acted upon by an external torque

Moment of inertia = mass x radius^2

Question 19

How does moment of inertia affect rotation and angular velocity

Answer 19

Decreasing moment of inertia (eg: tucking arms in, mass centred closer to radius of rotation) increases angular velocity
- increase in rate of rotation

Increasing moment of inertia (eg: spreading arms out, mass centred further from radius of rotation) decreases angular velocity Increasing

Question 21

Conservation of a angular momentum

Answer 21

Angular momentum of an object will remain constant unless acted upon by an external torque.
- moment of inertia increases = decreased angular velocity
- moment of inertia decreases = increased angular velocity

Question 22

Conservation of momentum

Answer 22

The total momentum within a system before a collision is equal to the total momentum of the system after the collision

Question 23

Principle of conservation of angular momentum

Answer 23

An objects angular momentum will remain constant unless acted upon by an external torque.

Question 24

Impulse and formula

Answer 24

Impulse is the change in momentum of an object

Impulse (I) = force (f) x time (t)

Question 25

What influences impulse (change in momentum)

Answer 25

A large force applied over a very short period of time A small force applied over a longer period of time

Question 26

How does impulse decrease risk of injury?

Answer 26

By increasing the amount of time over which the force is applied (i = force x time), it decreases the impact of the force on the athlete and therefore reduces likelihood of injury

Question 27

Speed and formula

Answer 27

How fast an object is travelling/ rate of motion Measured by distance travelled in a certain amount of time Speed = distance/ time

Question 28

Velocity and formula

Answer 28

Rate of motion in a specific direction (calculates changes in direction and time taken) Velocity = displacement/ time

Question 29

Newton’s first law

Answer 29

An object will remain at rest or in motion unless acted upon by an unbalanced or external force.

Question 30

Inertia

Answer 30

An object’s tendency to resist changes to its motion. The greater an object’s inertia, the harder it is to change its motion (to move or change direction of).

Question 32

Newton’s second law

Answer 32

Force = mass x acceleration Force = newtons Mass = kg Acceleration = m/s^2

Question 33

Newton’s second law example

Answer 33

To bat against a pitched softball, the player must apply a greater force than the ball’s momentum to change the ball’s direction and cause it to accelerate in the opposite direction The more force applied, the greater the acceleration of the ball

Question 34

Newton’s third law

Answer 34

For every reaction there will be an equal and opposite reaction When striking a softball, the ball applies an equal and opposite force onto the bat, making it bounce off and accelerate into the opposite direction.

Question 35

Equilibrium

Answer 35

The state in which all forces and torques acting upon and object are balanced. Could be stationary or at constant velocity.

Question 36

Static equilibrium

Answer 36

Object is completely motionless and all forces acting upon it are balanced. All horizontal and vertical forces or torques must add up to zero

Question 37

Equilibrium

Answer 37

The state in which all of the forces and torques acting upon a body are balanced (whether at constant velocity or when motionless)

Question 38

Dynamic equilibrium

Answer 38

When an object is moving at a constant velocity and all of the forces and torques acting upon it are balanced.

Question 39

Static equilibrium

Answer 39

When an object is motionless and all forces/ torques acting upon it are balanced

Question 40

Ways to increase stability

Answer 40

-increasing friction between body and surface -lowering centre of gravity -ensuring line of gravity is within base of support -increasing base of support

Question 41

Why might an athlete decrease stability

Answer 41

Athletes like swimmers or sprinters decrease stability by shifting their line of gravity to the edge of their base of support as it allows for them to accelerate into the pool or onto the track at a faster speed, allowing for a faster start in the race and overall faster time.

Question 42

First class levers

Answer 42

Have effort in the middle Example: header in soccer Axis: vertebrae/ cranium Effort: neck muscles Load: weight of the head

Question 43

Second class levers and example

Answer 43

Have load in the middle Make it easier to move heavy loads with relatively less force Eg: calf raises Axis: ankle joint Muscle/ effort: gastrocnemius/ calf muscle Load: body weight

Question 44

Third class lever and example

Answer 44

Fulcrum is in the middle Require a greater force to move a given load, but allow for a greater range of motion and speed Example: bicep curl Axis: elbow joint Load: weight in hand Effort: muscle attached to arm/ bone