# Force Flashcards Preview

## A Level PE Miss Rex > Force > Flashcards

Flashcards in Force Deck (17)
1
Q

What is the relationship between the centre of mass and the application of force ?

A

A force who’s line of application passes through the centre of mass causes the resulting motion to be linear
A force who’s line of application passes outside its centre of mass causes the resulting motion to be angular. Called an eccentric force = rotation = angular motion

2
Q

Define a scalar and vector quantity

A

Scalar - a scalar quantity has only magnitude e.g. speed, mass, distance
Vector - a vector quantity has both magnitude and direction e.g. displacement, velocity, acceleration, momentum, weight

3
Q

Give the formula for weight

A

Weight (N) = mass x gravitational force
Weight is a vector quantity

4
Q

Define both displacement and distance

A

Distance - Measured in metres. The path a body takes as it moves from the starting to finishing position. Scalar quantity.
Displacement- Measured in metres. Shortest route in a straight line between start and finish position. Vector quantity.

5
Q

Define speed

A

Speed - the rate of change of a position. Is a scalar quantity
Given by the formula - distance / time

6
Q

Define velocity

A

Velocity - Velocity refers to how fast a body travels in a certain direction. It is the ‘rate of change of displacement. It is a vector quantity.
Velocity = displacement (M) / time (s)

7
Q

Define acceleration

A

Acceleration - the rate of change of velocity. When velocity increases, positive acceleration occurs whilst when velocity decreases negative acceleration occurs.
Acceleration - change in velocity / time

8
Q

Define momentum ?

A

Is the product of mass and velocity of an object. It is a vector quantity.
Momentum (kg/ms) - mass(kg) x velocity (m/s)

9
Q

What is the conservation of momentum ?

A

This occurs when an object or a performer is in flight
When in flight neither mass nor velocity can be altered

10
Q

What are the 2 type of forces and their definitions ?

A

Internal forces - generated by the skeletal muscle
External forces - comes from outside the body

11
Q

Give examples of internal forces

A

In a layup the forces are generated by the gastrocnemius, quadriceps and gluteals that contract concentrically to plantarflex the ankle & extend the knee and hip in a jump

12
Q

Give examples of external forces

A

Air resistance, gravity, weight

13
Q

How can you categorise external forces ?

A

Horizontal forces - friction and air resistance
Vertical forces - gravity and weight

14
Q

What Is a reaction force ?

A

A force which is generated when 2 objects are in contact with each other
Newtons 3rd law - for every action there is an equal and opposite reaction

15
Q

What 2 types of friction forces are there ?

A

Static - force exerted when there is no motion between 2 objects. Force that keeps an object at rest
Sliding - When 2 bodies in contact have the tendency too slip / slide over one another. Friction acts in opposition to motion

16
Q

What 3 factors affect friction ?

A

1) The roughness of the surface
2) The mass of the object
3) Temperature of the 2 surfaces. Increase in temperature reduces the friction

17
Q

What 3 factors effect air resistance ?

A

The velocity of the moving object
The frontal cross sectional area of the moving body
The shape and surface characteristics of the moving body