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# Newton's 2nd Law Rockets mit Gravity If we fire a rocket vertically, its acceleration will be a bit less since it must struggle against gravity. For vertical ascent (neglecting air resistance):

• arocket = Ftotal ÷ mrocket

If the rocket moves vertically, it sees (experiences) two forces:

1. the upward thrust of 120 Newtons 2. the weight of the rocket
• weight = (rocket's mass) · (accel of gravity)
• weight = 1.5kg · 9.8m/s2
• weight ≈ 15N

## Solution:

1. State the unknown: Acceleration
2. State the givens: Force and Mass
3. State the equation you plan to use: Acceleration = Force ÷ Mass
4. Plug in values with units of measure: Acceleration = (120N – 15N) ÷ 1.5kg

A water bottle rocket has a mass of 0.248 kilograms. On Earth, this is a weight of 2.43 Newtons. When the water sprays out the bottom of the bottle rocket, it creates a starting thrust of 77 Newtons. Calculate the water rocket’s starting acceleration:

### Solution:

1. State the unknown:
2. State the givens:
3. State the equation you plan to use:
4. Plug in values with units of measure: