Lesson 3 Linear Motion

What is the definition of a scalar quantity?

• A quantity with both magnitude and direction

• A quantity with magnitude only

• A quantity that is always positive

• A quantity that changes with time

Answer explanation

A scalar quantity is defined as a quantity that has magnitude only, without any direction. This distinguishes it from vector quantities, which have both magnitude and direction. Therefore, the correct answer is 'A quantity with magnitude only'.

Which of the following is an example of a vector quantity?

• Distance

• Speed

• Time

• Displacement

Answer explanation

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

What is the SI unit of speed?

• Meters per second (m/s)

• Kilometers per hour (km/h)

• Miles per hour (mph)

• Centimeters per second (cm/s)

Answer explanation

The SI unit of speed is meters per second (m/s), which is the standard unit used in scientific contexts. Other units like kilometers per hour (km/h) and miles per hour (mph) are commonly used but are not SI units.

What does the term 'acceleration' refer to?

• The rate of change of velocity

• The distance covered in a straight line

• The rate of change of speed

• The total distance traveled

Answer explanation

The term 'acceleration' specifically refers to the rate of change of velocity, which includes both speed and direction. The other options describe distance or speed but do not capture the full definition of acceleration.

What is the formula for calculating average velocity?

• Average Velocity = Speed / Time

• Average Velocity = Displacement / Time

• Average Velocity = Distance / Time

• Average Velocity = Acceleration / Time

Answer explanation

Average velocity is defined as the total displacement divided by the total time taken. This distinguishes it from average speed, which uses total distance. Therefore, the correct formula is Average Velocity = Displacement / Time.

What does Newton's First Law of Motion state?

• For every action, there is an equal and opposite reaction

• Acceleration is proportional to the force applied

• Force equals mass times acceleration

• An object in motion stays in motion unless acted upon

Answer explanation

Newton's First Law of Motion states that an object in motion stays in motion unless acted upon by an external force. This means that without interference, objects will maintain their state of motion.

What is the definition of displacement?

• Distance traveled over time

• Distance covered in a straight line

• Total distance traveled regardless of direction

• Shortest distance between two points in a specified direction

Answer explanation

Displacement is defined as the shortest distance between two points in a specified direction. This distinguishes it from other measures like total distance traveled, which does not account for direction.

What is the SI unit of acceleration?

• Newton (N)

• Meters per second (m/s)

• Meters per second squared (m/s²)

• Kilometers per hour (km/h)

Answer explanation

The SI unit of acceleration is meters per second squared (m/s²), which measures the change in velocity per unit time. Other options like Newton (N) and kilometers per hour (km/h) are not correct for acceleration.

How is average speed calculated?

• Total distance / Total time

• Total displacement / Total time

• Total distance / Total velocity

• Total velocity / Total time

Answer explanation

Average speed is calculated by dividing the total distance traveled by the total time taken. Therefore, the correct choice is 'Total distance / Total time', as it accurately reflects this definition.

What is the relationship defined by Newton's Second Law of Motion?

• F = ma

• F = mv

• F = ma²

• F = m/a

Answer explanation

Newton's Second Law of Motion states that the force (F) acting on an object is equal to the mass (m) of the object multiplied by its acceleration (a), represented by the equation F = ma. This is the correct relationship.