1.
When an object's distance from another object is changing.
Correct Answer
A. It is in motion
Explanation
When an object's distance from another object is changing, it indicates that the object is in motion. Motion refers to the change in position of an object with respect to its surroundings over time. Therefore, the correct answer is "it is in motion."
2.
Speed equals distance divided by
Correct Answer
A. Time
Explanation
Speed is defined as the distance traveled per unit of time. Therefore, in order to calculate speed, one needs to divide the distance traveled by the time it took to cover that distance. This is why the correct answer is "time". Velocity, size, and motion are not directly related to the calculation of speed.
3.
When you know both the speed and direction of an object's motion, you know the
Correct Answer
D. Velocity of the object
Explanation
When you know both the speed and direction of an object's motion, you know the velocity of the object. Velocity is a vector quantity that includes both the magnitude (speed) and direction of an object's motion. So, knowing the speed and direction allows us to determine the velocity of the object.
4.
The rate at which velocity changes is called
Correct Answer
C. Acceleration
Explanation
Acceleration is the correct answer because it refers to the rate at which velocity changes. Velocity is a vector quantity that includes both speed and direction, so when the velocity of an object changes, it means either the speed or the direction or both are changing. Acceleration specifically measures the change in velocity, whether it is an increase or decrease in speed, a change in direction, or a combination of both. Therefore, acceleration is the appropriate term to describe the rate at which velocity changes.
5.
Which of these is an example of deceleration?
Correct Answer
C. A car approaching a red light
Explanation
Deceleration refers to the decrease in speed or velocity of an object. In this case, a car approaching a red light is an example of deceleration because as the car gets closer to the red light, it slows down and eventually comes to a stop. The other options do not involve a decrease in speed. A bird taking off for flight involves an increase in speed, a roller coaster moving down a steep hill involves a constant or increasing speed, and an airplane following a straight path implies a constant speed as well.
6.
To determine the acceleration rate of an object, you must calculate the change in speed during each unit of
Correct Answer
C. Motion
Explanation
To determine the acceleration rate of an object, you must calculate the change in speed during each unit of motion. This means that you need to measure the change in speed over a specific period of time while the object is in motion. By calculating this change in speed over time, you can determine the object's acceleration rate, which is the rate at which its velocity is changing. Therefore, the correct answer is motion.
7.
Average speed is
Correct Answer
D. The total distance traveled divided by the total time
Explanation
The correct answer is "the total distance traveled divided by the total time." Average speed is calculated by dividing the total distance traveled by an object by the total time it takes to cover that distance. It gives an overall measure of how fast an object is moving on average, regardless of the direction it is moving in. This differs from velocity, which is a vector quantity that includes both speed and direction. The other options provided in the question are not accurate definitions of average speed.
8.
A place or oject used for comparison to determine if something is in motion is called
Correct Answer
B. A reference point
Explanation
A reference point is used as a standard for comparison to determine if something is in motion. It provides a fixed location or object that remains stationary while other objects or locations are observed for motion. By comparing the position or movement of other objects to the reference point, it can be determined if they are in motion or not.
9.
On a graph showing distance versus time, a horizontal line represents an object that is
Correct Answer
D. Not moving at all
Explanation
A horizontal line on a distance versus time graph indicates that the object is not changing its position with respect to time. This means that the object is not moving at all. In other words, its speed is zero.
10.
Changing direction is an example of a kind of
Correct Answer
A. Acceleration
Explanation
Acceleration is the rate at which an object changes its velocity. When an object changes its direction, it is also changing its velocity, as velocity includes both speed and direction. Therefore, changing direction is an example of acceleration.
11.
A bicyclist travels 30 kilometers in two hours, her average speed is
Correct Answer
C. 15 km/h
Explanation
The average speed of the bicyclist can be calculated by dividing the total distance traveled (30 kilometers) by the total time taken (2 hours). Therefore, 30 km / 2 hours = 15 km/h.
12.
In an acceleration graph showing speed versus time, a straight line shows the acceleration is
Correct Answer
D. Constant
Explanation
In an acceleration graph showing speed versus time, a straight line indicates a constant acceleration. A straight line means that the speed is changing at a constant rate over time. If the line was increasing or decreasing, it would indicate that the acceleration is changing. Therefore, the correct answer is constant.