Flashcards in Forces Deck (27):

1

## What happens when you apply force to an object?

### It may stretch or change shape

2

## What is an elastic object?

### Any object that can go back to its original shape after the force has been removed

3

## What happens when an object changes shape?

### Work is done to the object and the energy is stored by the object as elastic potential energy

4

## What happens to elastic potential energy?

### It is converted to kinetic energy when the force is removed and the object returns to its original shape, eg a spring or elastic band bouncing back

5

## What is the equation and how does extension of elastic object work?

###
The extension is directly proportional to the force or load

Extension = metres

Force = Newtons

F=k x e

K is the spring constant - measured in Newtons per minute (N/m)

6

## When does this stop working?

###
There is a limit to the amount of force you can apply to an object to keep extension proportional

For small forces and extension are proportional

The limit of proportionality is the maximum force that the object can take and still extend proportionally

7

## Some examples of elastic potential?

###
Catapult

Trampoline

Scrunchies for hair

Elastic band

Spring

8

## What is the effect of balanced forces and unbalanced forces?

###
Balanced forces produce NO change in movement

Unbalanced forced change the speed and/or direction of objects

9

## What is a resultant force?

###
In most situations there are at least 2 forces acting on an object

The overall effect decides the motion of the object

If several forces acting then replace them with a single force which is the same as all the original forces acting together

This is the winning force between forces being applied to an object

It must have a direction

If original forces act along same line then overall effect found by adding or subtracting them

10

## What are the forces on a moving motorcycle or similar object?

###
Upthrust of the earth - contact force

Air resistance

Driving force - force of engine

Gravity or weight

11

## If the gravity is 9.8 and the mass of the bike and cyclist is 560 then what is the weight?

###
Gravity x mass = weight

9.8 x 560 = 5488N

12

## To make the bike accelerate what force is increased?

### Driving force

13

## As velocity increases what other force increases?

###
Air resistance increases and balances the driving when the acceleration stops

This creates a higher constant velocity

14

## What happens to a moving object when the forces on it change?

### A moving object will remain moving at a constant speed in a straight line unless upon by an external and unbalanced force.

15

## If a plane is traveling at steady velocity and the engine thrust is 8000N then what is the air resistance?

### 8000N

16

## If the mass of the aircraft and pilot is 670kg what is the force of uplift provided by the wings?

### 670 kg uplift

17

## If the pilot turns off the engine and the plane starts to fall then what force increases as it falls?

### Gravity or weight

18

## What is terminal velocity?

### Downward force of gravity equals the upward force of air resistance so the object neither accelerates nor decelerates

19

##
What is mass?

What is weight?

How do you calculate weight?

###
Mass is a measure of the amount of material an object is made of. Measured in kgs.

Weight is the force of gravity on an object. Measured in Newtons (N)

Weight = mass x gravitational force field

N = kg x N/kg

20

## Name types of forces?

###
Forces have a size and direction - vector quantities

Force = push, pull, twist

Change = shape, direction, speed

Contact force = forces that touch or make contact

Non contact force= act at a distance eg magnets

Force meter = Newton meter

21

## What is friction?

###
Friction resists the movement of an object

Measured in Newtons (N)

22

## Examples of friction

###
Friction is useful for:

Lighting a match

Shoelaces

Walking

Gymnastics

Writing

Friction is unwanted for:

Skiing

Surfing

Ice skating

Car engine

Space Shuttle

23

## What is falling?

###
An object falls through air

Accelerates due to gravity

Air resistance increases

Gravity and air resistance balance when equal

Object stops accelerating and moves at constant speed

This is terminal velocity

24

## How do we calculate speed and what is the difference between speed and velocity?

###
Speed (velocity) = distance/time - measured in metres per second

Speed is how fast you are going with no regard to direction- 30 mph

Velocity is speed and with direction specified - 30 mph north

25

## How do we calculate distance?

###
Distance = velocity x time

Measured in metres

26

## How do distance time graphs look and important notes?

###
Gradient = speed

Stationary or stopped = flat line

Constant speed = straight upward diagonal line - steeper is faster

Increasing speed = line curving upwards - increasing gradient

Decreasing speed = line curving up & levelling off - decreasing gradient

Downhill = going back towards starting point

27