Non-Uniform Motion (Cambridge (CIE) A Level Physics): Flashcards
Exam code: 9702
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Define drag force.
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Cards in this collection (14)
Define drag force.
A drag force is a force acting in the opposite direction to an object moving through a fluid (gas or liquid). Examples include air resistance and fluid resistance (viscous drag).
How does the magnitude of a drag force change as an object's speed changes?
It increases as the object speeds up and decreases as the object slows down.
For a car travelling at a constant velocity, what is true of the driving force and the frictional force acting on it?
The driving force is equal to the frictional force, so there is no resultant force acting on the car.
True or False?
As a car decelerates, the driving force is greater than the frictional force.
False.
When a car decelerates, the driving force is less than the frictional force, so the resultant force opposes the motion and the car slows down.
Air resistance occurs as an object moving through air .......... with the air particles.
Air resistance occurs as an object moving through air collides with the air particles.
State two factors that air resistance depends on.
The shape of the object
The speed at which it is travelling
Name two design features a racing cyclist uses to reduce air resistance.
A more streamlined body posture
Aerodynamically designed bicycle, clothing and helmet
Define terminal velocity.
Terminal velocity is the constant, maximum velocity reached by a falling object when the drag force acting on it becomes equal to its weight, resulting in zero resultant force.
For a body in free fall with no air resistance, what is the resultant force equal to, and what acceleration does the body experience?
The resultant force is equal to its weight, so the body accelerates at g, the acceleration of free fall.
As a falling object speeds up, what happens to the drag force, the resultant force and the acceleration acting on it?
Drag force increases
Resultant force decreases
Acceleration decreases
How is terminal velocity shown on a velocity-time graph?
The gradient (acceleration) decreases over time and reaches zero, so the graph becomes a horizontal line at a constant velocity.
True or False?
A skydiver moves upwards when their parachute is deployed.
False.
The skydiver decelerates to a lower terminal velocity; they do not move upwards.
Two skydivers of different mass jump from a plane. Which one reaches the greater terminal velocity, and why?
The skydiver with the greater mass, because they have a greater weight force, so a greater air resistance force is needed to balance it before terminal velocity is reached.
Terminal velocity is the .......... velocity that a falling body can reach.
Terminal velocity is the maximum velocity that a falling body can reach.
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