Physics Motion Quiz 05

Two radio-controlled cars move in one direction down a track. At each second, the cars spray a paint dot on the track to mark their position. The top-down view of the track is shown along with the position readings along the track. Which car had the highest average speed for its 5-second trip and why?

• Car 1; it is moving faster at the 2.5 second point.

• Car 1; it moves faster for more seconds.

• Car 2; it finishes further down the track.

• Car 2; it moves very fast in the last two seconds.

• Both are the same; they travel the same distance.

Answer explanation

Both cars traveled the same distance over the 5 seconds, resulting in the same average speed. The positions marked by the paint dots confirm that neither car outperformed the other in terms of distance covered.

Tags

NGSS.MS-PS3-1

A baseball pitcher throws a fastball at 42 m/s. If the batter is 18 m from the pitcher, approximately how much time does it take for the ball to reach the batter?

• 0.43 s

• 0.86 s

• 1.9 s

• 2.3 s

Answer explanation

To find the time, use the formula: time = distance / speed. Here, distance = 18 m and speed = 42 m/s. Thus, time = 18 m / 42 m/s = 0.4286 s, which rounds to approximately 0.43 s, making it the correct choice.

A race car driver travels at 110 meters per second for 20 seconds. How far did the driver travel during the 20-second time interval?

• 1,100 kilometers

• 2,200 kilometers

• 1.1 kilometers

• 2.2 kilometers

Answer explanation

To find the distance traveled, multiply speed by time: 110 m/s * 20 s = 2200 meters. Convert to kilometers: 2200 m = 2.2 km. Thus, the driver traveled 2.2 kilometers.

A salesperson drives the 215 miles from New York City to Washington, DC, in 4.5 hours. What was her average speed? (Round to the nearest whole number. Do not include units.)

Answer explanation

To find the average speed, divide the distance by time. Average speed = 215 miles / 4.5 hours = 47.78. Rounding to the nearest whole number gives 48.

An automobile travels between the 100-m and 250-m markers on a highway in 10 s. The average velocity of the automobile during this interval is:

• 10 m/s.

• 15 m/s.

• 25 m/s.

• 40 m/s.

Answer explanation

Average velocity is calculated as (final position - initial position) / time. Here, (250 m - 100 m) / 10 s = 15 m/s. Thus, the average velocity of the automobile is 15 m/s.

You run from your house to a friend's house that is 3 miles away in 30 minutes. You then immediately walk home, taking 1 hour on your return trip. What was your average speed in miles per hour for the entire trip? (Write the number without units.)

Answer explanation

Total distance = 3 miles (to friend's) + 3 miles (back home) = 6 miles. Total time = 30 minutes + 60 minutes = 90 minutes = 1.5 hours. Average speed = total distance / total time = 6 miles / 1.5 hours = 4 mph.

You run from your house to a friend's house that is 3 miles away in 30 minutes. You then immediately walk home, taking 1 hour on your return trip. What was your average velocity in miles per hour for the entire trip? (Write the number without units.)

Answer explanation

Average velocity is total displacement divided by total time. You run 3 miles to your friend's house and return, so displacement is 0 miles. Total time is 1.5 hours. Thus, average velocity = 0 miles / 1.5 hours = 0.

Consider the following Position vs. Time graph which represents the relationship between position and time for an object during the time interval shown. During which interval was the object at rest?

• A-B only

• B-C only

• C-D only

• A-B and C-D

Answer explanation

The object is at rest when the position vs. time graph is horizontal. In intervals A-B and C-D, the graph is flat, indicating no change in position, meaning the object is at rest during these intervals.

The Position vs. Time graph for an automobile is shown below. Which reason below might best explain the automobile’s change in motion at point X?

• the automobile slowed down

• the automobile sped up

• the road was no longer straight

• the road became less steep

Answer explanation

At point X, the slope of the Position vs. Time graph decreases, indicating the automobile is covering less distance over time. This suggests that the automobile slowed down, making it the best explanation for the change in motion.

Tags

NGSS.MS-PS2-2

What is the average speed of the object for the time interval from 1 minute to 5 minutes?

• 0.75 m/min

• 1.00 m/min

• 1.25 m/min

• 3.00 m/min

Answer explanation

To find the average speed, divide the total distance by the total time. If the object travels 5 m in 4 minutes (from 1 to 5 minutes), the average speed is 5 m / 4 min = 1.25 m/min, which is the correct answer.

Tags

NGSS.MS-PS3-1