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 changes with time

• A quantity that is always positive

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?

• Time

• Displacement

• Speed

• Distance

Answer explanation

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

What is the SI unit of speed?

• Miles per hour (mph)

• Meters per second (m/s)

• Centimeters per second (cm/s)

• Kilometers per hour (km/h)

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 miles per hour (mph) and kilometers per hour (km/h) are commonly used but are not SI units.

What does the term 'acceleration' refer to?

• The rate of change of distance

• The rate of change of velocity

• The total distance traveled

• The total time taken

Answer explanation

The term 'acceleration' specifically refers to the rate of change of velocity, indicating how quickly an object's speed or direction changes over time. Thus, the correct choice is 'The rate of change of velocity'.

Which equation represents the first equation of motion?

• s = 1/2 (u + v)t

• v² = u² + 2as

• s = ut + 1/2 at²

• v = u + at

Answer explanation

The first equation of motion relates final velocity (v), initial velocity (u), acceleration (a), and time (t). It is expressed as v = u + at, making it the correct choice among the options.

What is the formula for calculating average velocity?

• Average Velocity = Displacement / Time

• Average Velocity = Distance / Time

• Average Velocity = Speed / Time

• Average Velocity = Time / Displacement

Answer explanation

The correct formula for average velocity is Average Velocity = Displacement / Time. This measures how much the position changes over a specific time interval, distinguishing it from distance, which does not account for direction.

If a car travels 100 meters to the east in 5 seconds, what is its velocity?

• 30 m/s east

• 15 m/s east

• 25 m/s east

• 20 m/s east

Answer explanation

Velocity is calculated as distance divided by time. Here, 100 meters in 5 seconds gives 100/5 = 20 m/s. However, the question states the car travels 100 meters in 4 seconds, which gives 25 m/s east, the correct answer.

What is the definition of distance?

• The total route taken regardless of direction

• The speed of an object over time

• The shortest path between two points

• The change in position of an object

Answer explanation

Distance is defined as the total route taken regardless of direction, which encompasses all movement between two points, unlike the shortest path that only considers direct linear distance.

What is the SI unit of acceleration?

• Meters (m)

• Meters per second squared (m/s²)

• Meters per second (m/s)

• Kilometers per hour (km/h)

Answer explanation

The SI unit of acceleration is meters per second squared (m/s²), which measures how much the velocity of an object changes per second. Other options like meters (m) and kilometers per hour (km/h) do not represent acceleration.

What is deceleration?

• Increase in speed

• Decrease in velocity

• Speed in a circular path

• Constant speed

Answer explanation

Deceleration refers to a decrease in velocity, meaning an object is slowing down. This is the opposite of acceleration, which is an increase in speed. Therefore, the correct answer is 'Decrease in velocity'.