Practise explaining how drag, weight and upthrust change resultant force and acceleration, and how motion reaches terminal speed when forces balance.
A box in air slides with increasing speed down a rough slope from point P to point Q.
The slope surface exerts a constant frictional force on the box.
As the box moves from P to Q, there are changes to the magnitudes of its acceleration and the total resistive force acting on it.
Which row describes the changes?
magnitude of
acceleration
magnitude of
total resistive
force
increases
decreases
decreases
decreases
increases
increases
decreases
increases
A football is kicked so that it moves vertically upwards through the air.
What is the variation in the air resistance and the resultant force acting on the ball as it moves vertically upwards?
air resistance
resultant force
decreases
decreases
decreases
increases
increases
decreases
increases
increases
The graph shows the variation with time of the speed of a raindrop falling vertically through air.
Which statement is correct?
The acceleration decreases to produce a steady speed.
The acceleration increases as the speed increases.
The air resistance decreases as the speed increases.
The resultant force increases as the speed increases.