Practise explaining how drag, weight and upthrust change resultant force and acceleration, and how motion reaches terminal speed when forces balance.
The cylinder in (b) is released from the string at time . The cylinder falls, from rest, vertically downwards through the water. Assume that the upthrust acting on the cylinder remains constant as it falls.
State the name of the force that acts on the cylinder when it is moving and does not act on the cylinder when it is stationary.
State and explain the variation, if any, of the acceleration of the cylinder as it falls downwards through the water.
The ball in (b) leaves the toy at point A and moves vertically upwards through the air. Point B is the position of the ball when it is at maximum height h above point A , as illustrated in Fig. 3.2.
Fig. 3.2 (not to scale)
The gravitational potential energy of the ball increases by 0.60 J as it moves from A to B .
When there is air resistance, the ball takes time T to move from A to B .
State and explain whether the time taken for the ball to move from A to its maximum height will be more than, less than or equal to time T if there is no air resistance.