1.18 describe experiments to investigate the forces acting on falling objects, such as sycamore seeds or parachutes

- Make/obtain 5 paper parachutes that each have a different surface area.
- Drop each of the 5 parachutes 3 times from a given height (e.g. 2m)
- Time how long it takes for the parachute to reach the floor
- Find a mean time for each parachute (add up each of the 3 times and divide the number by 3). You should now have 5 values.
- Plot the values in a graph with size of parachute along the X-axis (in cm²) and time along the Y-axis (in s)
- Draw a line of best fit

1.36 understand that:  the universe is a large collection of billions of galaxies  a galaxy is a large collection of billions of stars  our solar system is in the Milky Way galaxy

32. - The universe contains many galaxies
    - Each galaxy contains many stars
    - Each star has its own solar system
    - Our solar system is in a galaxy called the Milky Way
    

1.35 use the relationship between orbital speed, orbital radius and time period

0. orbital speed = 2  x π  x orbital radius time period /time period
   
   v = 2 x π x r / t
   

1.34 describe the differences in the orbits of comets, moons and planets

Planets and moons both orbit in circle paths
Comets orbit in ovals known as ellipticals

1.33 explain that gravitational force:  causes moons to orbit planets  causes the planets to orbit the sun  causes artificial satellites to orbit the Earth  causes comets to orbit the sun

if an object entres the field of another objects gravitational force, it will travel around the object in an orbit.

This causes...
- planets to orbit the sun
- artificial satellites to orbit earth
- comets to orbit the sun
- moons to orbit planets

1.32 understand gravitational field strength, g, and recall that it is different on other planets and the moon from that on the Earth

Gravitational field strength (g) is how strongly something pulls an object towards it. 

On Earth it is 9.8 (rounded to 10)

Earth has a higher gravitational field strength than the moon. This is because they have different masses, the Earth has more mass than the moon, therefore the Earth has a bigger gravitational field strength than the moon - the bigger the planet/object (as comets and stars can have g too) the bigger the gravitational field strength.

1.31 describe elastic behaviour as the ability of a material to recover its original shape after the forces causing deformation have been removed

Elastic behaviour is the idea that when you stretch an elastically object it will return to its original shape after the forces stretching it stop stretching it.

For example...

When you stretch an elastic band and then let it go it pings back to regain its original shape and size.

1.30 understand that the initial linear region of a force-extension graph is associated with Hooke’s law

Hooke's law stated that the force needed to extend (or compress) a spring is proportional to the distance it is extended (or compressed).

a force extension graph shows how much a material stretches in proportion to how much force is applied.

The initial linear region is the straight diagonal line showing a linear correlation between force and extension, basically meaning that they increase at the same rate (this is Hooke's law).

At some point, the graph will curve, this is when the spring reaches its elastic potential, the extension and force are no longer proportional.

1.29 describe experiments to investigate how extension varies with applied force for helical springs, metal wires and rubber bands

- attach a spring to a Newton metre and measure its length
- Add a weight (ideally 50g) to the end of the spring and measure again
- continue to add weights and take measurements
- do this up to 400g
- plot your results on a graph

by plotting a graph of results you can see that extension increases with force

1.28 understand that the upward forces on a light beam, supported at its ends, vary with the position of a heavy object placed on the beam

the best way to explain this is by using an example...

If a 10N weight were to be placed on a beam, the trestles (P and Q) would have to increase their upward force by 10N


if the mass was positioned closer to Q, Q would have to exert more force than P. Similarly, if the mass was positioned closer to P, P would have to exert more force than Q.

1.27 know and use the principle of moments for a simple system of parallel forces acting in one plane

The Principle of Moments states that an object will be balanced if the sum of 
the clockwise moments is equal to the sum of the anticlockwise moments. 
This means that the moments must balance either side.
e.g.

Clockwise moments = anticlockwise moments
moment = force x distance from pivot

W x 4 = 0.8 x 24 = 19.2
W = 19.2 / 4
W = 4.8N

1.26 recall that the weight of a body acts through its centre of gravity

The centre of gravity of an object is where all its weight acts through

1.25 know and use the relationship between the moment of a force and its distance from the pivot

9. moment = force × perpendicular distance from the pivot 
   

1.24 demonstrate an understanding of Newton’s third law

Newtons third law states that 'each force has an equal and opposite force'. one way in which this could be demonstrate is through ice skating. if you throw a snowball whilst you are on ice skates, you  involuntarily go backwards a little. This is newtons third law in action. When you throw the snowball, you are exerting a force forward, at the same time an equal force is acting in the opposite direction, usually this force is hardly noticeable, if all. Since you are standing on ice that has very little friction, you will go backward.

1.23 use the relationship between force, change in momentum and time taken

9. force = change in momentum / time taken
   

1.22 use the conservation of momentum to calculate the mass, velocity or momentum of objects

use this triangle...

or, if your not a fan of the triangle...

momentum = mass x velocity

velocity = momentum / mass

mass = momentum / velocity

example question: if a ball with a mass of 0.5g is thrown at 50m/s, what is its momentum?

0.5 x 50 = 25N

1.21 use the idea of momentum to explain safety features

force = change in momentum / time

safety features aim to reduce the force acting upon the human. If the momentum of the vehicle is decreased, the force felt by the human will decrease. similarly, if the time taken for momentum to change is increased, the overall force is decreased.

crumple zones in cars are designed to decrease the time it takes for the momentum of the car to reach zero, this will result in the passenger feeling less force

air bags also decrease the force felt by the passenger


to understand better (don't write in exam!)...

if you jump with your knees locked on landing, you will feel more force than if you jumped with your knees bent on landing. You feel less force when your knees are bent because you take more time to reach zero momentum than if your knees are locked... try it :)

1.20 know and use the relationship between momentum, mass and velocity

9. 
   momentum = mass × velocity
   
   p=m×v 
   

1.13 find the resultant force of forces that act along a line

The resultant force is the overall force acting upon an object. The best way to describe it is through diagrams, for example...

1.7 determine acceleration from the gradient of a velocity-time graph

I find it helps to remember 'rise over run', all this means is that in order to work out the acceleration all you need to do is do velocity / time.

In the example above...

The acceleration represented by the sloping line is 2m/s². This is because the object increases its velocity from 0m/s to 8m/s in 4s therefore its acceleration is 8 ÷ 4 = 2m/s^2.