Unit 3: Force & Motion

What is the SI unit for speed?

• m

• s

• m/s

• s/m

Answer explanation

Feedback: Speed is typically measured in meters per second, or m/s.

Tags

NGSS.MS-PS3-1

What are the axes on a distance-time graph?

• the x-axis is time and the y-axis is distance

• the x-axis is distance and the y-axis is time

• the x-axis is time and the y-axis is speed

• the x-axis is speed and the y-axis is time

Answer explanation

Feedback: On a distance-time graph, the x-axis is time and the y-axis is distance.

If a train goes at a constant speed of 40 miles per hour for one hour, then at a constant speed of 50 miles per hour for two hours, what is its instantaneous speed at the beginning of the last hour of its trip?

• 40 mph

• 45 mph

• 47 mph

• 50 mph

Answer explanation

Feedback: The instantaneous speed of the train at the beginning of the last hour is 50 mph.

What does a straight, sloped line on a distance-time graph represent?

• changing speed

• constant speed

• instantaneous speed

• zero

Answer explanation

Feedback:  A straight, sloped line on a distance-time graph represents constant, unchanging speed.

Tags

NGSS.MS-PS3-1

Which best describes the velocity of a person on a merry-go-round?

• constant

• increasing

• zero

• continuously changing

Answer explanation

Feedback: The velocity of an object moving in a circle is continuously changing.

The graph gives the distance each girl swam with time. Who swam at a constant speed for the entire race?

• only Julie

• Julie and Mary

• Mary and Kathy

• only Kathy

Answer explanation

Feedback: Straight line graphs of distance over time that do not change direction show constant speed. Mary and Kathy were swimming at a constant speed for the entire race.

Tags

NGSS.MS-PS3-1

What was Julie’s average speed (in meters/second) after 20 minutes?

• 0.33 m/s

• 3 m/s

• 20 m/s

• 48 m/s

Tags

NGSS.MS-PS3-1

What was Julie’s average speed (in meters/second) after 10 minutes?

• 0.67 m/s

• 1.5 m/s

• 24 m/s

• 40 m/s

Tags

NGSS.MS-PS3-1

What was Julie’s average speed (in meters/second) after 30 minutes?

• 0.33 m/s

• 0.67 m/s

• 1.5 m/s

• 216 m/s

Tags

NGSS.MS-PS3-1

What happened to Julie during the time between 10 and 20 minutes?

• Her speed decreased.

• She finished the race.

• She stopped swimming.

• Her speed increased.

Answer explanation

Feedback: Since she did not swim any farther during that time, she must have stopped swimming.

Tags

NGSS.MS-PS3-1