Mechanics Flashcards
What are Scalar Quantities?
Scalar quantities have MAGNITUDE ONLY
What are Vector Quantities?
Vector quantities have MAGNITUDE and DIRECTION
What is magnitude?
Magnitude represents the size or extent of something, so scalar and vector quantities both indicate the size of them
How can Vector quantities be represented?
Through an ARROW, where the size of the arrow represents magnitude, and the direction in which it points represents the direction
Scalar Quantities examples…
- Mass
- Current
- Time
- Distance
- Energy
- Speed
Vector Quantities examples…
- Force
- Velocity
- Weight
- Displacement
How does one combine PARALLEL Vectors?
They simply ADD UP
How does one combine non-parallel Vectors?
One can use the TIP TO TAIL rule or the PARALLELOGRAM rule
What does the Gradient represent in a Distance Time graph?
Speed
What does the gradient represent in a speed time graph?
Acceleration
How does one find the distance travelled in a speed time graph?
Calculate the area under the graph…
How to work it out…
S = D/T
D = ST
D = 10 x 5 (eg)
D = 50m
How does one calculate the speed at a single point in the graph?
One must use a TANGENT, which is a line Parallel to the point in the graph
what is a contact force
A contact force is a force acting between two objects where the objects are PHYSICALLY TOUCHING
What are some examples of contact forces?
Friction, Air resistance, Tension, Normal contact force
what is a non-contact force
Non-contact forces are forces that act between two objects that are PHYSICALLY SEPARATED.
What are some examples of non-contact forces?
Gravity, Electrostatic force, Magnetic
What is Newton’s First Law?
Newton’s first law states that ‘A body will not change its motion unless acted on by an external force’
What is Inertia?
Inertia is related to Newton’s 1st Law. Object with a GREATER MASS have MORE INERTIA, so it takes MORE FORCE to change their motion.
Inertia is the tendency of an object to RESIST a change in MOTION
What is Inertial Mass?
Inertial Mass is the MEASURE of an object’s RESISTANCE to ACCELERATION
What is the equation for Weight?
W = M x G
N) = (kg) x (N/KG
What is the equation for Density?
D = M ÷ V (kg/cm^3) = (kg) ÷ (cm^3)
What is Newton’s second law of Motion?
If a force accelerates an object, the rate of acceleration is directly proportional to the mass of the object
F = MA
What is the equation for Force?
F = M x A
(N) = (kg) x (m/s^2)
What is the equation for Acceleration?
Acceleration = (Final Speed - Start Speed)/ Time
A = ΔV/ΔT
What does constant force aim to prove in F = MA?
If the force is constant, acceleration is inversely proportional mass
What does constant mass aim to prove in F = MA?
If the mass is constant, acceleration is directly proportional to force
What does directly proportional mean?
If you double one, the other one doubles too
What does inversely proportional mean?
If you double one, you half the other one too
If a force of 10N is applied to a ball of mass 1kg, how fast will it move? Will it be faster that a ball of 0.05kg?
The 1kg ball will move 10 m/s^2, while the 0.05kg one will move 20 times faster, at 200m/s^2
What is Newton’s 3rd Law?
Whenever two objects INTERACT, they exert EQUAL and OPPOSITE FORCES on EACHOTHER
When labelling force on an object, where does the arrow start?
At the centre of mass.
Remember…
The forces may be EQUAL and OPPOSITE, however the EFFECTS may not be
What is the key condition when considering Newton’s Third law?
The forces must be of the SAME TYPE, eg. Gravity against Gravity, REACTION AGAINST REACTION
What is the Braking Distance?
The distance a vehicle travels under the BRAKING FORCE
What is the Thinking Distance?
The distance a vehicle travels during the THINKING FORCE