Projectile Motion Flashcards
Projectile motion (definition)
Projectile (definition)
Movement of a body through the air following a curved flight path under the force of gravity
A body that is launched into the air losing contact with the ground surface such as discuss or long jumper
The horizontal distance travelled by a projectile is affected by three factors:
What are they (including small explanation)
Angle of release
- The optimum angle is dependant upon release height and landing height
Speed of release
- Due to Newton’s 2nd Law the horizontal distance a projectile travels is primarily affected by speed of release.
- Greater the velocity of a projectile the greater the horizontal displacement travelled
Height of release
- A greater height results in an increased in horizontal displacement as gravity is acting on a mass.
Parabolic flight path (definition)
Parabolic flight path occurs when…
Example
A flight path symmetrical about its highest point caused by the dominant weight force of a projectile
Weight is the dominant force
Means air resistance is small.
The shot put has a high mass and travels through the air at a low velocity, with a relative small frontal cross-sectional area and a smooth surface
Non-parabolic flight path (definition)
A non-parabolic flight path occurs when…
Example
A flight path asymmetrical about its highest point caused by the dominant weight force of air resistance
Air resistance is the dominant force
A badminton shuttle has a very low mass and travels at high velocities with a relative uneven surface; this causes an increase in air resistance, and causes the shuttle to fly in a non-parabolic flight path
Parabola (definition)
A uniform curve that is symmetrical about it highest point
Free body diagrams
These are simple sketches to give a snapshot of the forces acting upon the projectile at a specific time. It demonstrates: (4)
There are 3 phases when drawing the diagram:
Key points to remember:
- which forces are acting
- where they originate from
- relative sizes
- direction in which they are acting
- Start of flight
- Mid flight
- End of flight
a. Weight will not change during these phases
b. Air resistance WILL change as it is dependent upon velocity
Free body diagram - Shot put vs Shuttlecock
Parallelogram of forces (definition)
How to draw a parallelogram of forces (4 steps)
What does a parallelogram of forces look like (diagram)
A parallelogram illustrating the theory that a diagonal drawn from the point where forces are represented in size and direction shows the resultant force acting
- On the shot put indicate where the COM of the projectile is
- Add in the air resistance line and weight (remember to show the direction and which is the dominant force)
- Add broken parallel lines to weight and air resistance to create a parallelogram
- Draw a diagonal line from the COM to the opposite corner with a double arrow and label it ‘resultant force’
Resultant Force (definition)
What it means
Possible outcomes of resultant forces (2)
The sum of all forces acting on a body or the net force acting on a projectile
A resultant force shows the acceleration of a projectile and the direction in which the acceleration occurs. It will also indicate the flight path
- if the resultant force is close to the weight arrow, weight is more dominant, so the flight path is more parabolic
- if the resultant force is closer to the air resistance arrow, air resistance is more dominant, so flight path will be non-parabolic
Parallelogram of forces - Shuttlecock
The Bernoulli principle (2 parts)
Lift forces are important as … (2 parts)
- is the creation of an additional lift force on a projectile in flight
- the higher the velocity of air flow, the lower the surrounding pressure.
the overall effect of additional lift is that there is an increased amount of time the projectile hangs in the air;
- which will extend the flight path and the horizontal distance covered.
Bernoulli Principle - Aerofoils - What is it?
The science behind it - aerofoils (5)
An aerofoil has a curved upper surface and a flat underneath surface
- When there is a projectile in the air, the air flow is forced to part, however, it needs to meet at the end of the projectile at the same time.
- The curved upper surface of the aerofoil means that air has a further distance to travel; whilst the flat underneath surface has less of a distance to travel
- This means that the velocity over the upper curved surface needs to be higher.
- As velocity increases pressure decreases.
- As all fluids move from an area of high pressure to an area of low pressure, a pressure gradient is formed which results in a lift force.
Bernoulli Principle – Lift Force (definition)
As well as having upward lift forces it is possible to have what is known as downward lift force. An example of this is…
Bernoulli Principle - Key terms – Angle of Attack
An additional force created by a pressure gradient forming on opposing surfaces of an aerofoil moving through fluid
This will work if the aerofoil shape is inverted, this is used in F1 cars and track cycling. By increasing the downward force the car and bike are held onto the track at high speeds around corners.
The most favourable angle of release for a projectile to optimise lift force due to the Bernoulli principle
Practical example of aerofoils - f1 car (5)
Front wing funnels air down through the narrow space underneath the car’s chassis
The spoiler acts as an inverted aerofoil, forcing air underneath to travel a further distance
Air velocity underneath the car is increased, creating areas of low pressure
A pressure gradient is formed, additional downward lift force is created
The result is increased grip and friction around corners at high speeds
Magnus effect (definition)
Creation of an additional Magnus force on a spinning projectile which deviates from the flight path
Air flow diagram - Topspin
Flight path diagram - Topspin
Air flow diagram - Hook
Flight path diagram - Hook
Air flow diagram - Sidespin slice
Flight path diagram - Sidespin slice
