shape or direction
Forces acting on a body of mass can change its speed, shape or direction.
1.10 identify different types of force such as gravitational or electrostatic
All bodies of mass enact a force, known as gravitational force. Larger bodies of mass have more gravitational force than smaller ones, e.g. the Sun has gravitational force that is strong enough to keep the solar system in orbit; but a human doesn't have a strong enough gravitational field to attract any matter.
Forces can be contact or non-contact. Non-contact forces include drag, magnetic, electrostatic and gravitational; while contact forces involve direct contact and include friction, tension, normal, upthrust and air resistance.
1.11 distinguish between vector and scalar quantities
A vector has both direction and magnitude, e.g. acceleration
A scalar has only direction, no magnitude, e.g. speed
1.12 understand that force is a vector quantity
Force has both direction and magnitude; for it to be a force it must be acting in a direction, and it must be a measurable quantity (thus magnitude)
1.13 find the resultant force of forces that act along a line
The resultant force is the overall force acting in a direction on the object. This can be calculated by subtracting forces acting in opposite directions.
1.14 understand that friction is a force that opposes motion
Every action has an equal and opposite reaction- this is Newton's 3rd law of motion, which means that an object in motion will experience an opposite force in response, such as air resistance or friction.
1.15 know and use the relationship between unbalanced force, mass and
acceleration:
force = mass × acceleration
F = m × a
1.16 know and use the relationship between weight, mass and g:
weight = mass × g
W = m × g
1.17 describe the forces acting on falling objects and explain why falling objects
reach a terminal velocity
A falling object is affected by the vertical forces of gravity, which pulls it towards the Earth's centre of mass, and air resistance or drag, which works in the opposite direction of gravity. When it is falling and the forces are imbalanced-the force of gravity is greater than the air resistance- the object is accelerating. As the object increases in velocity, the air resistance increases, meaning that at a certain point, the drag will be equivalent to the gravitational force. When the force up = the force down, there is no acceleration, meaning the object will be falling at a constant velocity, known as terminal velocity.
1.18 describe experiments to investigate the forces acting on falling objects, such
as sycamore seeds or parachutes
Sycamore seeds:
Seeds should be collected and the length of wing measured. They should be dropped and timed, and a graph drawn to show the relationship between length of wing and speed.
Parachutes:
Dropping same-weighted objects attached to parachutes of different sizes from the same height, and measuring the time it takes for the object to reach the ground. This is investigating the air resistance on the parachute, and should show that with increased surface area, the object will move more slowly.
1.19 describe the factors affecting vehicle stopping distance including speed,
mass, road condition and reaction time
The stopping distance is increased by increased speed, as it takes space and time to decelerate;
Higher mass of vehicle means that when it is in motion it has more momentum, therefore requiring more space to stop with the same amount of force applied;
Wet or otherwise slippery roads decrease the friction with the wheels, making it more difficult to stop and increasing the stopping distance;
Reaction time affects stopping distance because it increases the time spent travelling at full speed and the distance travelled before the vehicle begins to decelerate. (Can be affected by tiredness, visibility, sobrerity, etc.)
1.20 know and use the relationship between momentum, mass and
velocity:
momentum = mass × velocity
p = m × v
1.21 use the idea of momentum to explain safety features
Safety features in a car-
Seatbelt: Extends the time over which the person's body decelerates as it stretches, reducing impact force.
Crumple Zone: Force is exerted over a larger period of time and therefore reducing the impact force and damage to the person
Air bags: Change in momentum of the driver is spread out over a longer time, reducing impact force
1.22 use the conservation of momentum to calculate the mass, velocity or
momentum of objects
Momentum remains the same before and after a collision, so with certain variables given, mass, velocity or momentum can be calculated
1.23 use the relationship between force, change in momentum and time
taken:
force = change in momentum/time taken
1.24 demonstrate an understanding of Newton’s third law
Newton's third law is that every action has an equal and opposite reaction. This means that two bodies of mass interacting will exert forces on each other. For example, when a ball is dropped it will exert a force on the ground, and the ground will exert a force on the ball, leading to a resultant force that causes the ball to bounce up again. Another example is sitting on a chair: You exert a force on the chair, but the chair exerts an equal force back: supporting and holding you up.
1.25 know and use the relationship between the moment of a force and its
distance from the pivot:
moment = force × perpendicular distance from the pivot
1.26 recall that the weight of a body acts through its centre of gravity
The centre of gravity of an object is the point at which the mass is evenly dispersed at every direction from it. The centre of gravity of an object can be placed on a pinpoint and it won't overbalance due to uneven forces: it has a resultant force of 0 in every direction.
1.27 know and use the principle of moments for a simple system of
parallel forces acting in one plane
Moment = Force x Distance
Anticlockwise and clockwise moments must be equal, so for a pivot to be balanced the distance from pivot x force must be equal on both sides of the pivot.
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
Momentum is force multiplied by distance, so when the distance is altered, the force exerted must change to accommodate to the momentum, which remains the same (because clockwise and anticlockwise moment must be equal). If a heavy object is placed in the centre of a light beam that is supported at its ends, an equal force will be exerted on both supports; but if it is closer to support A than support B, more force will be exerted on support A. This is like the previous, but upside down. It can be easier to imagine the force between the supports as the pivot and the supports as the weights.
1.29 describe experiments to investigate how extension varies with applied force
for helical springs, metal wires and rubber bands
Set up your apparatus so the object (spring, wire, rubber band, etc.) is suspended from a clamp on a weighted stand. Measure the length of your object before any force has been applied to find its natural length. Add a hanging mass and record the extension. Add an extra mass, record the extension and repeat, adding one mass at a time. Once you're done, repeat the entire experiment and record your results to draw an average and make your results more reliable. Graph the results to see how the extension varies.
1.30 understand that the initial linear region of a force-extension graph is
associated with Hooke’s law
Before the elastic object reaches its elastic limit, the quantity of force applied is proportional to the object's extension. This means that when it is graphed, it will produce a straight line. Hooke's law states that extension is proportional to force, which we can see clearly when we investigate the elasticity of different objects.
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 objects and materials are able to be stretch when a force is applied, then return to their original shape once the force is removed.
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