Question

in the image seen here, a fish (10n) swims in an aquarium (20n) filled with water (40n) upon a table (50n). identify the action/reaction force pairs seen here and place them properly in the image. assume that down is negative in all cases.

Explanation:

Step1: Analyze Fish-Water Force Pair

The fish exerts a downward force (action) on the water, and the water exerts an upward force (reaction) on the fish. The fish's weight is 10N, so the action force is -10N (downward) and the reaction force is +10N (upward).

Step2: Analyze Aquarium-Water-Fish System and Table Force Pair

The total weight of the aquarium (20N) + water (40N) + fish (10N) is \(20 + 40 + 10 = 70N\). This system exerts a downward force (action) on the table, so that's -70N. The table exerts an upward reaction force of +70N on the system.

Step3: Analyze Table and Ground Force Pair

The table (with the system on it) has a total weight? Wait, no, the table's own weight is 50N, but the force from the system is 70N? Wait, no, the normal force from the table to the system is 70N, so the action force from the system on the table is 70N downward (-70N), and the table exerts +70N upward. Then, the table's total downward force on the ground is its own weight (50N) plus the 70N? Wait, no, the problem's force values: the table is 50N, aquarium 20N, water 40N, fish 10N. Wait, maybe the table and the ground: the table (with the 70N force from the system) and its own weight? No, the action-reaction pairs:

1. Fish and water: Fish pushes water down (-10N), water pushes fish up (+10N).
2. Aquarium - water - fish system (total weight 20 + 40 + 10 = 70N) pushes table down (-70N), table pushes system up (+70N).
3. Table (with the 70N force from the system) and the ground: Wait, the table's own weight is 50N, but the force from the system is 70N, so the total downward force on the ground from the table is 70N (from the system) plus 50N (table's weight)? No, no, action-reaction pairs: the table exerts a force on the ground, and the ground exerts a force on the table. Wait, the total downward force on the ground is the table's weight (50N) plus the 70N? No, the problem's given force values have +120N, -120N, +70N, -70N, +10N, -10N. Wait, maybe I miscalculated. Wait, the table's weight is 50N, and the system's weight is 70N, so total downward force on the ground is \(50 + 70 = 120N\) (action, -120N), and the ground exerts an upward reaction force of +120N on the table.

So the three action - reaction pairs:

• Fish - Water: -10N (fish on water) and +10N (water on fish).
• System (aquarium + water + fish) - Table: -70N (system on table) and +70N (table on system).
• Table - Ground: The table (with the 70N from the system and its own 50N? No, the table's total downward force is 70N (from the system) plus its own weight? Wait, no, the action-reaction between table and ground: the table exerts a downward force (action) on the ground, which is the sum of the force from the system (70N) and its own weight (50N)? Wait, \(70 + 50 = 120N\), so action force -120N, reaction force +120N (ground on table).

Now, matching the given force values: +120N, -120N, +10N, -10N, +70N, -70N.

So:

• Fish - Water: -10N (fish to water) and +10N (water to fish).
• System - Table: -70N (system to table) and +70N (table to system).
• Table - Ground: -120N (table to ground) and +120N (ground to table).

Answer:

• Fish - Water: Action (-10N), Reaction (+10N)
• System (Aquarium + Water + Fish) - Table: Action (-70N), Reaction (+70N)
• Table - Ground: Action (-120N), Reaction (+120N)