Physics worksheet focusing on forces, motion, and acceleration, featuring problems involving car and rocket scenarios.

Let’s solve each part step by step.

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Problem 1: Car on level road

Given:
- Mass of car, m = 925 kg
- Applied force (forward), F_applied = 3706 N
- Coefficient of friction, μ = 0.40
- Gravity, g = 9.8 m/s² (standard value)

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A) Calculate the force weight of the car.

Weight is the force due to gravity:
W = m × g
W = 925 kg × 9.8 m/s²
W = 9065 N

✔ So, weight = 9065 N

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B) Calculate the force friction acting on the car.

Friction force = μ × Normal Force
On a level road, normal force = weight = 9065 N
So, F_friction = 0.40 × 9065 N
F_friction = 3626 N

✔ Friction force = 3626 N

*(Note: This opposes motion, so it acts backward.)*

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C) What is the net force acting on this car?

Net force = Forward force – Friction force
F_net = 3706 N – 3626 N
F_net = 80 N

✔ Net force = 80 N forward

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D) Calculate the acceleration of the car.

Use Newton’s Second Law:
F_net = m × a → a = F_net / m
a = 80 N / 925 kg
a ≈ 0.0865 m/s²

Rounded to 3 significant figures: 0.0865 m/s²

✔ Acceleration = 0.0865 m/s²

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Problem 2: Rocket launched upward

Given:
- Mass of rocket, m = 550,000 kg
- Upward thrust force, F_thrust = 5,800,000 N
- Gravity, g = 9.8 m/s²

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A) What is the downward force caused by gravity on the rocket at liftoff?

That’s just the weight:
W = m × g
W = 550,000 kg × 9.8 m/s²
W = 5,390,000 N

✔ Downward gravitational force = 5,390,000 N

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B) What is the net force acting on the rocket at liftoff?

Net force = Upward thrust – Downward weight
F_net = 5,800,000 N – 5,390,000 N
F_net = 410,000 N upward

✔ Net force = 410,000 N upward

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C) Calculate the acceleration of the rocket as it leaves the launch pad.

Again, use F_net = m × a → a = F_net / m
a = 410,000 N / 550,000 kg
a ≈ 0.745 m/s²

✔ Acceleration = 0.745 m/s² upward

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D) As the rocket moves upwards, the engine thrust remains constant, but the mass decreases rapidly. How does the acceleration change? Why?

As fuel burns, the rocket gets lighter → mass decreases.

Thrust stays same, but mass goes down → acceleration increases (since a = F/m).

Also, air resistance and gravity decrease slightly with height, but main reason is decreasing mass.

✔ Answer: Acceleration increases because the rocket’s mass decreases while thrust stays constant.

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E) Does the astronaut experience greater or lesser g-forces as the rocket continues to rise? Explain using Newton’s laws.

“g-force” here means how heavy the astronaut feels — which depends on the normal force from the seat pushing up on them.

As acceleration increases (from part D), the net force on the astronaut increases → the seat must push harder to accelerate them upward.

By Newton’s 2nd law: F_seat - mg = ma → F_seat = m(g + a)

Since ‘a’ is increasing, F_seat increases → astronaut feels heavier → experiences greater g-forces.

✔ Answer: Greater g-forces, because acceleration increases, so the seat pushes harder on the astronaut.

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Final Answer:

Problem 1:
A) 9065 N
B) 3626 N
C) 80 N forward
D) 0.0865 m/s²

Problem 2:
A) 5,390,000 N
B) 410,000 N upward
C) 0.745 m/s² upward
D) Acceleration increases because mass decreases while thrust is constant.
E) Greater g-forces, because increasing acceleration requires a larger upward force from the seat.