Review and Understanding Speed and Motion

Ava, Arjun, and Mason are having a friendly race at school! Oliver wants to cheer them on and also figure out how fast they are running. What is the SI unit of speed that Oliver should use to measure their running speed?

• Meter

• Meter per second

Answer explanation

The SI unit of speed is meter per second (m/s), which measures the distance traveled in meters for each second of time. Other options like meter, kilometer, and second do not represent speed.

Tags

NGSS.MS-PS3-1

Maya, Zoe, and Aiden are racing from Maya's house to their school in a straight line. As they compare notes about their journey, which of the following quantities describing their trip is a vector?

• Displacement

• Time

Answer explanation

Displacement is a vector quantity as it has both magnitude and direction, representing the shortest path from the initial to the final position. In contrast, speed, distance, and time are scalar quantities.

Harper, Daniel, and Anika are having a contest to spot the most interesting things outside their window. Harper notices a parked car and decides to plot its position on a distance-time graph. If the car doesn't move at all, what would a horizontal line on the graph represent?

• Stationary object

• Increasing speed

Answer explanation

A horizontal line on a distance-time graph indicates that the distance remains constant over time, meaning the object is stationary. Therefore, the correct answer is 'Stationary object'.

Charlotte and David decide to have a friendly race in their cars. After the race, they compare the distance each drove and the time it took. Which formula should they use to calculate their average speed?

Answer explanation

The correct formula for average speed is \( \text{Speed} = \frac{\text{Distance}}{\text{Time}} \). This means speed is calculated by dividing the total distance traveled by the total time taken.

Grace, Samuel, and Mia are having a race to see who can spot the fastest moving objects! They record the speeds in different units. Which of the following is NOT a unit of speed?

• cm/s

Answer explanation

The unit m²/s represents area per time, not speed. Speed is measured in units like m/s, km/h, and cm/s, which indicate distance traveled over time.

Tags

NGSS.MS-PS3-1

Oliver and Abigail are having a friendly race on their bicycles. Oliver covers a distance of 100 meters in just 5 seconds! What is Oliver's average speed?

• 50 m/s

• 20 m/s

Answer explanation

To find average speed, divide distance by time. Here, average speed = 100 meters / 5 seconds = 20 m/s. Thus, the correct answer is 20 m/s.

Tags

NGSS.MS-PS3-1

Nora and Mia are having a friendly race at the park. Nora cycles a distance of 400 m in 50 seconds. What is Nora’s average speed?

• 400 m/s

• 8 m/s

Answer explanation

To find average speed, use the formula: speed = distance/time. Here, distance = 400 m and time = 50 s. Thus, average speed = 400 m / 50 s = 8 m/s. Therefore, the correct answer is 8 m/s.

Sophia and Grace are having a friendly cycling race to a nearby town. Sophia covers a distance of 30 km in 2 hours. What is her average speed in km/h?

• 15 km/h

• 28 km/h

Answer explanation

To find the average speed, divide the distance by the time. Here, 30 km ÷ 2 hours = 15 km/h. Thus, the average speed is 15 km/h.

Charlotte, Aria, and Olivia are on a road trip! Charlotte drives her car at a steady speed of 60 km/h. If she keeps driving for 3 hours, how far will she travel?

• 120 km

• 180 km

Answer explanation

To find the distance traveled, use the formula: distance = speed × time. Here, speed is 60 km/h and time is 3 hours. Thus, distance = 60 km/h × 3 h = 180 km. Therefore, the correct answer is 180 km.

Kai and Nora are having a friendly race in the park. Kai jogs at a speed of 5 m/s for 12 seconds. What distance does Kai cover during his run?

• 24 m

• 60 m

Answer explanation

To find the distance covered, use the formula: distance = speed × time. Here, speed = 5 m/s and time = 12 s. Thus, distance = 5 m/s × 12 s = 60 m. Therefore, the correct answer is 60 m.