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Chapter 4: Dynamics: Force and Newton's Laws of Motion

College Physics (Urone)
Pages: 127 - 166

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60 Questions for Chapter 4: Dynamics: Force and Newton's Laws of Motion

  1. Suppose the mass of a fully loaded module in which astronauts take off from the Moon is 10,000 kg. The thrust of its engines is 30,000 N.

    Found on Page 161
  2. A rock is thrown straight up. What is the net external force acting on the rock when it is at the top of its trajectory?

    Found on Page 159
  3. (a) Give an example of different net external forces acting on the same system to produce different accelerations. (b) Give an example of the same net external force acting on systems of different masses, producing different accelerations. (c) What law accurately describes both effects? State it in words and as an equation.

    Found on Page 160
  4. The rocket sled shown in Figure 4.33 accelerates at a rate of 49.0 m/s2. Its passenger has a mass of 75.0 kg.

    Found on Page 161
  5. If the acceleration of a system is zero, are no external forces acting on it? What about internal forces? Explain your answers.

    Found on Page 160
  6. If a constant, nonzero force is applied to an object, what can you say about the velocity and acceleration of the object?

    Found on Page 160
  7. The gravitational force on the basketball in Figure 4.6 is ignored. When gravity is taken into account, what is the direction of the net external force on the basketball—above horizontal, below horizontal, or still horizontal.

    Found on Page 160
  8. When you take off in a jet aircraft, there is a sensation of being pushed back into the seat. Explain why you move backward in the seat—is there really a force backward on you? (The same reasoning explains whiplash injuries, in which the head is apparently thrown backward.)

    Found on Page 160
  9. A device used since the 1940 s to measure the kick or recoil of the body due to heart beats is the “ballistocardiograph.” What physics principle(s) are involved here to measure the force of cardiac contraction? How might we construct such a device?

    Found on Page 160
  10. A brave but inadequate rugby player is being pushed backward by an opposing player who is exerting a force of 800 N on him. The mass of the losing player plus equipment is 90.0 kg, and he is accelerating at 1.20 m/s2 backward. (a) What is the force of friction between the losing player’s feet and the grass? (b) What force does the winning player exert on the ground to move forward if his mass plus equipment is 110 kg?

    Found on Page 161

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