Chapter 2 Answers:
Review Questions:
1. Here is another way of putting the law of inertia: an object in motion tends to retain its speed and direction (velocity) in the absence of any outside force imposed on it. That is, it is 'natural' for an object to maintain its velocity.
4. Because the bird is is moving along with the branch and the earth at the same velocity. This is the idea of relative motion that we learned in class (remember the question 'is the book moving'?).
5. A straight line according to Newton's 1st law.
7. Acceleration is inversely proportional to mass
9. The acceleration remains the same
11. because the ratio between its weight and mass (W/m) is a constant (g).
13. size and weight
15. the faster object
16. His weight is greater (see #13)
23. They have different masses as well (recall the bowling ball and the pin example from class)
25. No: see #23
27. An external force (a force that comes from outside the system)
Exercises:
1. Shake 'em both up! The box with feathers has less mass and thus less inertia. It'll be easier to shake (accelerate back and forth). The box with iron won't be easy to shake (accelerate) at all.
5.
7.
9.
Problems:
1. 4000 N
2. 200 N, backwards
5. the same: 1 m/s2
9. 480 N