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

1.31 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...

1.9 describe the effects of forces between bodies such as changes in speed, shape or direction

changes in speed
- when an object is stationary it has the same forces pushing down (gravity) and up (the surface the object is on)
- when an object is at a constant speed it has equal upward and downward forces but also equal forward and backward forces.
- when an object is accelerating, it has equal upward and downward forces and also forward and backward forces, the forward force is larger than the backward force
- when an object is decelerating it has equal upward and downward forces and also forward and backward forces, the backward force is larger than the forward force

changes in shape
- changes in shape due to force affect momentum, for example, crumple zones change shape due to the force they are hit, this decreases the force felt on passengers

changes in direction
- whichever direction the force is greatest in (resultant force), the object will travel in that direction. For example, if an object has a larger forward force than backward force, it will accelerate, likewise, if an object has a larger backward force than forward force, it will decelerate.

1.10 identify different types of force such as gravitational or electrostatic

gravity: acting downwards (weight is a force due to gravity)

upthrust: acting upwards

Drag and friction: acting against the movement

gravitational: Gravity or gravitational forces are forces of attraction, like the Earth pulling on you and keeping you on the ground

electrostatic: An electrostatic force is a kind of force that originates from a static (non-moving) electric charge

1.19 describe the factors affecting vehicle stopping distance including speed, mass, road condition and reaction time

9. stoping distance = thinking distance + breaking distance
   thinking distance is the person takes to react to needing to stop ( basically their reaction time, the time it takes them to press the break)
   factors affecting thinking distance…
   

   • conditions of driver, e.g. tiredness or drugs

   • distractions, e.g. children or something in the road

   
   breaking distance is the time it takes for the car to reach 0 m/s once the break has been pressed
   factors affecting breaking distance…

   • conditions of the breaks and tyres, e.g. how old/worn they are

   • weather conditions, e.g. if the weather is bad

   • the speed the car is traveling at

1.17 describe the forces acting on falling objects and explain why falling objects reach a terminal velocity

when an object falls, it is also accelerating, this means that gravity (the force acting downward) is larger than air resistance (the force acting upwards)

Terminal velocity is when gravity and air resistance become equal (i.e. there is no resultant force). 

When an object reaches terminal velocity, it has also reached its maximum speed.

1.16 know and use the relationship between weight, mass and g

weight = mass X g

g stands for gravitational constant (this is 9.8, or 10, on earth)

1.15 know and use the relationship between unbalanced force, mass and acceleration

0. force = mass × acceleration 
   
   F=m×a