Speed And Motion Flashcards
What does acceleration measure?
The rate of change of velocity (how much you velocity changes each second)
What is the equation for acceleration?
Acceleration = change in velocity/time
a = v-u/t
What is Newton’s first law?
An object will remain at rest or at a constant velocity unless a resultant force acts on it.
What is the resultant force?
The sum of all forces acting on an object.
(Force is a vector quantity so a resultant force must have a direction e.g 7N to the right)
What is Newton’s second law?
The acceleration of an object is directly proportional to the resultant force acting on it but inversely proportional to the mass of the object.
What equation links resultant force with the acceleration and mass of an object?
Acceleration = resultant force/mass
F = ma OR a = F/m
(F is resultant force not just force)
What’s Newton’s 3rd law?
If object A exerts a force on object B, then object B must exert a force on object A that is equal but opposite in direction.
What acronym can be used to answer a question on terminal velocity?
Forces acting
Resultant force
Acceleration
Velocity
Describe the motion of a falling object. (Use FRAV)
• Initially only weight is acting on the object.
• Resultant force acts downwards
• Therefore; object accelerates downwards
• Meaning velocity increases
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• As velocity increases, drag increases while weight stays constant.
• Resultant force still acts downwards but decreases.
• So downward acceleration decreases
• Meaning velocity continues to increase at a decreasing rate.
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• Drag continues to increase with velocity until it becomes equal to weight.
• Resultant force is now zero
• Object no longer accelerates
• Velocity is now constant (terminal velocity)
What is thinking distance?
Thinking distance is the distance travelled between seeing the hazard and applying the braking force.
What is braking distance?
Braking distance is the distance travelled under the braking force.
What the equation links stopping distance with braking distance and thinking distance?
Thinking distance + breaking distance = stopping distance
