Question

1. a car is driving north at a steady speed. it makes a gradual 90° left - turn without losing speed, then continues driving to the west. draw a motion diagram, using the particle model, showing the cars velocity vectors as seen from a helicopter hovering over the highway.
2. a toy car rolls down a ramp, then across a smooth, horizontal floor. draw a motion diagram, using the particle model, showing the cars velocity vectors.
3. density is the ratio of an objects mass to its volume. would you expect density to be a vector or a scalar quantity? explain.

multiple - choice questions

1. a student walks 1.0 mi west and then 1.0 mi north. after - ward, how far is she from her starting point? a. 1.0 mi b. 1.4 mi c. 1.6 mi d. 2.0 mi
2. you throw a rock upward. the rock is moving upward, but it is slowing down. if we define the ground as the origin, the position of the rock is __ and the velocity of the rock is __ a. positive, positive b. positive, negative c. negative, positive d. negative, negative
3. which of the following motions could be described by the motion diagram of figure q1.20? a. a hockey puck sliding across smooth ice. b. a cyclist braking to a stop. c. a sprinter starting a race. d. a ball bouncing off a wall.
4. which of the following motions is described by the motion diagram of figure q1.21?

Explanation:

Step1: Analyze question 18

The student's movements form a right - angled triangle. Use the Pythagorean theorem $d = \sqrt{x^{2}+y^{2}}$, where $x = 1.0$ mi and $y = 1.0$ mi.
$d=\sqrt{(1.0)^{2}+(1.0)^{2}}=\sqrt{1 + 1}=\sqrt{2}\approx1.4$ mi

Step2: Analyze question 19

The rock is above the ground (origin), so the position is positive. It is moving upward, so the velocity is positive.

Step3: Analyze question 20

In the motion diagram of Figure Q1.20, the dots are getting closer together, indicating a decrease in speed. A cyclist braking to a stop has a decreasing speed.

Step4: Analyze question 21

Since the figure for Q1.21 is not shown completely, we assume based on the general analysis of options. An airplane braking to a stop after landing has a decreasing speed and a motion diagram with dots getting closer together.

Answer:

1. B. 1.4 mi
2. A. positive, positive
3. B. A cyclist braking to a stop
4. B. An airplane braking to a stop after landing