Question

1. what force does a soccer ball apply to a persons foot if the ball experiences a 1000 n force?
2. a 20 kg box rests on a table.

a. identify the three action - reaction force pairs involved in the box sitting on the table.
b. what force does the earth exert on the box?
c. what force does the box exert on the earth?

Explanation:

1.

Step1: Apply Newton's third law

Newton's third law states that for every action, there is an equal and opposite reaction. When the foot exerts a force on the ball, the ball exerts an equal - magnitude force on the foot.
If the force on the ball \(F_{ball}=1000\ N\), then the force on the foot \(F_{foot}\) (by the ball) is related as \(F_{foot}=-F_{ball}\) (the negative sign indicates the opposite direction). But in terms of magnitude, \(|F_{foot}| = |F_{ball}|\)

• First pair: The force of the box pulling up on the Earth (action) and the force of the Earth pulling down on the box (reaction) (gravitational force pair).
• Second pair: The force of the box pushing down on the table (action) and the force of the table pushing up on the box (normal force pair).
• Third pair: The force of the table pushing down on the Earth (action) and the force of the Earth pushing up on the table (reaction).

Step1: Use the formula for gravitational force

The formula for gravitational force is \(F = mg\), where \(m = 20\ kg\) and \(g=9.8\ m/s^{2}\)
\(F=mg=20\ kg\times9.8\ m/s^{2}\)

Answer:

\(1000\ N\)

2.

a.