Question

physics 9 | unit 2 lesson 19 | velocity lab (day 2)
objective: i can collect data to determine how height affects an objects impact velocity when in freefall and will use this data to determine how impact velocity is affected by changing height.
do now

1. a box is moving across a surface while experiencing balanced forces. classify the boxs state of motion.

______static equilibrium
______dynamic equilibrium
______acceleration
justify your response in one sentence.

1. a cart was traveling down the road while experiencing balanced forces. explain what happens to the cart when those forces are no longer balanced.

1. a feather and a brick are both dropped from a height of 10 meters. how fast do these objects accelerate towards the earth? explain how you know.

Explanation:

1.

Step1: Recall the definitions

• Static Equilibrium: Object is at rest.
• Dynamic Equilibrium: Object is moving at constant velocity.
• Acceleration: Object's velocity is changing.

Since the box is moving (not at rest) and has balanced forces (so velocity is constant), it is in dynamic equilibrium.

Step2: Justify

Balanced forces mean no net force. By Newton's first law, an object in motion with no net force moves at constant velocity (dynamic equilibrium).

2.

When forces are no longer balanced, there is a net force. By Newton's second law ($F = ma$), a net force ($F
eq0$) causes acceleration ($a=\frac{F}{m}$, $m$ is mass of cart). So the cart will accelerate (its velocity will change).

3.

In the absence of air resistance (assuming ideal free - fall as in basic physics problems), all objects near the Earth's surface accelerate at $g = 9.8\ m/s^{2}$. This is a fundamental result of gravitational physics near Earth (derived from Newton's law of gravitation and $F = ma$, where $F = mg$ for an object of mass $m$ near Earth's surface).

Answer:

1. Dynamic Equilibrium. Justification: Balanced forces mean no net force, so object moves at constant velocity (dynamic equilibrium).
2. The cart will accelerate (its velocity will change) because a net force (when forces are unbalanced) causes acceleration ($F = ma$).
3. Both accelerate at $9.8\ m/s^{2}$. In ideal free - fall (no air resistance), all objects near Earth’s surface have acceleration $g = 9.8\ m/s^{2}$ (from $F = mg$ and $F = ma$).