4.3 Newton’s Second Law of Motion: Concept of a System

Net external force, mass, and acceleration tied together, choosing the system boundary, and weight as gravity acting on mass.

College Physics 2e, 4.3 Newton’s Second Law of Motion: Concept of a System

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5 exercises

4.3 Exercise 11

You may assume data taken from illustrations is accurate to three digits.

A 63.0-kg sprinter starts a race with an acceleration of $4 . \text{20 m} /\text{s}^{2}$ . What is the net external force on him?

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4.3 Exercise 13

You may assume data taken from illustrations is accurate to three digits.

A cleaner pushes a 4.50-kg laundry cart in such a way that the net external force on it is 60.0 N. Calculate the magnitude of its acceleration.

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4.3 Exercise 17

(a) If the rocket sled shown in the figure starts with only one rocket burning, what is the magnitude of its acceleration? Assume that the mass of the system is 2100 kg, the thrust T is $2.59 \times 10^{4}$ N, and the force of friction opposing the motion is known to be 650 N. (b) Why is the acceleration not one-fourth of what it is with all rockets burning?

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4.3 Exercise 21

The rocket sled shown in the figure accelerates at a rate of $49.0 \text{ m}/\text{s}^{2}$ . Its passenger has a mass of 75.0 kg. (a) Calculate the horizontal component of the force the seat exerts against his body. Compare this with his weight by using a ratio. (b) Calculate the direction and magnitude of the total force the seat exerts against his body.

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4.3 Exercise 23

The weight of an astronaut plus their space suit on the Moon is only 250 N. How much do they weigh on Earth? What is the mass on the Moon? On Earth?

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