Linear Motion MCQ 1

Momentum and Force

• Momentum (p) is the product of an object's mass (m) and velocity (v): p = mv
• Unit of momentum is kg.ms^-1
• Principle of Conservation of Momentum: 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) causes acceleration, and F = ma
• Unit of force is Newton (N), where 1 N gives a mass of 1 kg an acceleration of 1 ms^-2
• 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

Vectors and Scalars

• Vector quantity: has both magnitude and direction (e.g. Displacement and momentum)
• 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

Distance, Speed, and Velocity

• Distance (s) is a measure of how far one point is from another
• Speed (v) is the distance travelled per unit time, and is a scalar quantity
• Velocity (v or u) is the rate of change of displacement with respect to time, and is a vector quantity

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, all objects near the earth's surface will fall with an acceleration due to gravity 'g'

Equations of Motion

• a = acceleration (ms^-2)
• u = initial velocity (ms^-1)
• v = final velocity (ms^-1)
• s = displacement (m)
• Equations: v = u + at, s = ut + 0.5at^2, v^2 = u^2 + 2as