Raising and Lowering

1

A box is lowered at constant velocity A box is lowered at constant velocity. Does the acceleration depend on the velocity? What is the net force on the box? Draw a force diagram for the box. Acceleration = rate of change in velocity = 0 for any size constant velocity (5 – 5 = 0, 10 – 10 = 0, etc.) The net force = mass x acceleration = 0 velocity Acceleration = 0

2

A box is raised at constant velocity. Is the acceleration +, -, or 0 A box is raised at constant velocity. Is the acceleration +, -, or 0? What is the net force on the box? Draw a force diagram for the box. Acceleration = rate of change in velocity = 0 since velocity does not change The net force = mass x acceleration = 0 velocity Acceleration = 0

3

A box is lowered with uniformly increasing speed and more negative velocity. Is the acceleration +, -, or 0? Is the net force on the box, up, down or zero? Draw a force diagram for the box. Acceleration is (-) since the velocity is becoming more negative The net force = mass x acceleration which is downwards since acceleration is downwards. acceleration velocity

4

A box is raised with uniformly increasing speed and more positive velocity. Does the acceleration depend on the velocity? Is the net force on the box, up, down or zero? Draw a force diagram for the box. Acceleration is (+) since the velocity is becoming more positive The net force = mass x acceleration which is upwards since acceleration is upwards. acceleration velocity

5

A box is lowered with uniformly decreasing speed and less negative velocity. Draw a motion diagram for the box. Is the net force on the box, up, down or zero? Draw a force diagram for the box. Acceleration is positive, e.g. velocity might change from -10 to -5, an increase of +5. The net force = mass x acceleration which is upwards since acceleration is upwards. acceleration It takes a net upward force to slow the descent of the box. velocity

6

A box is raised with uniformly decreasing speed and less positive velocity. Draw a motion diagram for the box. Is the net force on the box, up, down or zero? Draw a force diagram for the box. Acceleration is negative, e.g. velocity might change from +10 to +5, a change of -5. The net force = mass x acceleration which is downwards since acceleration is downwards. acceleration velocity