10 Questions
Which of the following statements is correct concerning a body moving at constant speed that is always changing directions, e.g. a body moving in a circle?
The body has constant speed
Which quantity represents the change in position with respect to time?
Velocity
In the absence of air resistance, all objects near the Earth's surface will fall with an acceleration due to what force?
'g' force
What is the rate of change of velocity with respect to time known as?
'a' force
According to the Principle of Conservation of Momentum, what is true about the total momentum before and after an interaction in a closed system?
They are always equal in magnitude.
What is the relationship between force and acceleration according to Newton's Second Law of Motion?
$F = ma$
In Newton's Third Law of Motion, what does it mean when it says 'for every action there is an equal and opposite reaction'?
The action and reaction forces have the same magnitude but opposite directions.
What is the relationship between momentum and velocity?
$mv = p$
What does Newton's First Law of Motion state about a body's motion?
A body remains at rest or in uniform motion unless acted upon by an external force.
If three forces keep a particle at rest, what can be said about the resultant of any two of them compared to the third force?
They are equal in magnitude but opposite in direction
Study Notes
Vectors and Scalars
- A vector quantity has both magnitude and direction (e.g., displacement and momentum).
- A scalar quantity has magnitude only (e.g., distance and time).
- The triangle and parallelogram law are used to find the direction of the resultant of two vectors.
- Trigonometry and Pythagoras theorem can be used to find perpendicular components of a vector.
Distance and Speed
- Distance (s) is a measure of how far one point is from another.
- Speed (v) is the distance travelled per unit time, s = d / t, unit = m/s.
- Speed is a scalar quantity with no direction.
Displacement and Velocity
- Displacement (s) is distance in a given direction.
- Velocity (v or u) is the rate of change of displacement with respect to time, velocity = displacement / time, unit = m/s.
Acceleration
- Acceleration (a) is the rate of change of velocity with respect to time, a = (v - u) / t.
- A body has an acceleration even if its speed remains constant if it is changing directions.
- In the absence of air resistance, objects near the earth's surface will fall with an acceleration due to gravity 'g'.
Equations of Motion
- a = acceleration (m/s²)
- u = initial velocity (m/s)
- v = final velocity (m/s)
- s = displacement (m)
- v = u + at
- s = ut + (1/2)at²
- v² = u² + 2as
Mass and Momentum
- Mass (m) is a measure of the amount of matter in a body, unit = kg.
- Momentum = mass × velocity, p = mv, unit = kg m/s.
- Principle of Conservation of Momentum: The total momentum before an interaction is equal to the total momentum after, within a closed system, m1u1 + m2u2 = m1v1 + m2v2.
Force and Newton's Laws
- A force (F) is something that causes acceleration, F = ma.
- Unit of force = Newton (N), 1 N is the force that gives a mass of 1 kg an acceleration of 1 m/s².
- Newton's Laws of Motion:
- Law 1: A body remains at rest or continues moving at constant velocity unless acted upon by a resultant external force.
- Law 2: The rate of change of momentum is proportional to the applied force and takes place in the direction of the force, F ∝ dp/dt.
- Law 3: For every action, there is an equal and opposite reaction.
Learn about vectors and scalars, including their definitions and how to find the direction of the resultant of two vectors using the triangle and parallelogram law. Explore the concepts of distance as a measure between two points and speed as the distance covered over time.
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