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AS Mechanics Quiz #5

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  • The normal reaction force acts perpendicular to the surface in contact
    True – By definition.
  • The acceleration vector always points in the same direction as velocity
    False – It can be opposite (deceleration).
  • The resultant of two perpendicular forces is found using Pythagoras’ theorem
    True – Vector addition applies.
  • An object thrown vertically upward experiences a constant upward force
    False – Gravity acts downward throughout.
  • For an object moving with uniform acceleration, velocity-time graph is a straight line
    True – Indicates constant acceleration.
  • The direction of the weight vector always points vertically downward
    True – Weight acts due to gravity.
  • If acceleration is zero, velocity must be zero
    False – Velocity can be constant and non-zero.
  • The area under a force-displacement graph represents work done
    True – Work is force times displacement in direction of force.
  • The magnitude of acceleration is the slope of a velocity-time graph
    True – Slope = acceleration.
  • If an object’s speed increases, its acceleration is positive
    False – Acceleration direction depends on the chosen coordinate system.
  • When two objects collide, the forces they exert on each other are equal and opposite
    True – Newton’s Third Law.
  • The symbol "u" in SUVAT equations stands for initial velocity
    True – It includes speed and direction.
  • Displacement can be negative depending on chosen coordinate system
    True – Direction matters.
  • The acceleration due to gravity is approximately "9.8 m/s²"
    True – This is the accepted standard near Earth’s surface.
  • The net force is the vector sum of all forces acting on an object
    True – It determines motion.
  • In a particle model, rotation is ignored
    True – Particle has no size or rotation.
  • Speed is a scalar and velocity is a vector
    True – Velocity has direction, speed does not.
  • An object moving in a circle at constant speed has zero acceleration
    False – Direction changes, so acceleration is centripetal.
  • Velocity and speed are the same if the direction is ignored
    True – Speed is the magnitude of velocity.
  • The weight of an object increases with mass
    True – Weight "W = mg" depends on mass.
  • A force acting on a stationary object will always cause it to move
    False – If forces are balanced, the object may remain at rest.
  • The velocity of a particle is zero at its maximum height during vertical motion
    True – Velocity changes sign here.
  • The equation "F = ma" relates force, mass, and acceleration
    True – It’s Newton’s Second Law.
  • In vertical projectile motion, the object’s speed is zero at the highest point
    False – Speed is zero only if it momentarily stops, but velocity changes direction.
  • A displacement-time graph with a constant positive gradient shows constant velocity
    True – Gradient represents velocity.
  • Frictional forces always oppose motion or attempted motion
    True – That is their nature.
  • The tension in a light inextensible string is the same throughout its length
    True – This is a common assumption in mechanics.
  • The unit of force is the newton, abbreviated as "N"
    True – Standard SI unit of force.
  • The displacement of a particle is the shortest distance from the initial to final position
    True – Displacement is a vector between two points.
  • If the resultant force on a body is zero, the body must be at rest
    False – It may move at a constant velocity.
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