Physics Motion Quiz 12

Which of the following is a vector quantity?

• distance (d)

• displacement (∆x)

• speed (s)

• time (t)

• duration (∆t)

Answer explanation

Displacement (∆x) is a vector quantity as it has both magnitude and direction, representing the change in position. In contrast, distance, speed, time, and duration are scalar quantities, lacking direction.

Which of the following is NOT a scalar quantity?

• 5 mph

• 10 Newtons

• 2 g

• -15 cm/s

• 20 pounds

Answer explanation

-15 cm/s is a vector quantity because it has both magnitude and direction (indicating speed and direction of motion). The other options are scalar quantities, which only have magnitude.

Tags

NGSS.MS-PS3-1

NGSS.MS-PS3-2

The speed versus time graph shows the motion of an object for three minutes. What is the average speed of the object for the entire motion?

• 1.33 meters/min

• 2.66 meters/min

• 3.0 meters/min

• 4.0 meters/min

• 6.0 meters/min

Answer explanation

To find the average speed, calculate the total distance traveled and divide it by the total time. The graph indicates a total distance of 12 meters over 3 minutes, resulting in an average speed of 4.0 meters/min.

Tags

NGSS.MS-PS3-1

Which pair of graphs represents an object that is moving at a constant speed? (The displacement graph should be interpreted as a position-time graph.)

• A

• B

• C

• D

Answer explanation

Graph B shows a straight line, indicating constant speed, as the position changes uniformly over time. In contrast, other graphs depict varying slopes, suggesting acceleration or deceleration.

Tags

NGSS.MS-PS3-1

You are traveling with a constant speed of 0.5 m/s in a cart that suddenly starts to roll downhill and speed up at 1.5 m/s/s. What is your velocity after speeding up for 7 seconds? (Write the number without units.)

Answer explanation

To find the final velocity, use the formula: final velocity = initial velocity + (acceleration × time). Here, initial velocity = 0.5 m/s, acceleration = 1.5 m/s², and time = 7 s. Thus, final velocity = 0.5 + (1.5 × 7) = 11 m/s.

You are traveling at a constant speed of 30 mph through rush hour traffic. Finally the traffic congestion clears up and you can start speeding up. If your speed increases 2 mph/s, how many seconds will it take to reach 60 mph? (Write the number without units.)

Answer explanation

To reach 60 mph from 30 mph, you need to increase your speed by 30 mph. At an acceleration of 2 mph/s, it takes 30 mph ÷ 2 mph/s = 15 seconds. However, the answer choices indicate 0 seconds, which is incorrect.

A train travels 6 meters in the first second of travel, 6 meters in the second second of travel, and 6 meters again during the third second. Its acceleration is:

• 0 m/s/s

• 6 m/s/s

• 12 m/s/s

• 18 m/s/s

• other

Answer explanation

The train travels the same distance (6 meters) in each second, indicating constant speed. Since there is no change in velocity, the acceleration is 0 m/s/s.

A car starts from rest and after seven seconds it is moving 42 m/s. What is the car’s average acceleration?

• 0.17 m/s/s

• 1.67 m/s/s

• 6 m/s/s

• 7 m/s/s

Answer explanation

Average acceleration is calculated using the formula: (final velocity - initial velocity) / time. Here, (42 m/s - 0 m/s) / 7 s = 6 m/s². Thus, the car’s average acceleration is 6 m/s/s.

Tags

NGSS.MS-PS2-2

A car moves in a straight line. At t = 1 s its speed is 35 km/hr, at t = 2 s its speed is 40 km/hr, and at t = 3 s its speed is 45 km/hr. What is the car’s acceleration?

• 5 km/hr/s

• 10 km/hr/s

• 25 km/hr/s

• 35 km/hr/s

• 45 km/hr/s

Answer explanation

To find acceleration, use the formula: a = (final speed - initial speed) / time. From t=1s to t=3s, speed changes from 35 km/hr to 45 km/hr over 2 seconds. Thus, a = (45 - 35) / 2 = 5 km/hr/s.

A car accelerates at 2 m/s/s. Assuming the car starts from rest, how much time does it need to accelerate to a speed of 20 m/s?

• 2 seconds

• 5 seconds

• 10 seconds

• 20 seconds

• 40 seconds

Answer explanation

To find the time, use the formula: time = (final speed - initial speed) / acceleration. Here, time = (20 m/s - 0 m/s) / 2 m/s² = 10 seconds. Thus, the car needs 10 seconds to reach 20 m/s.