Knowledge Check - Changes in Speed

If velocity is constant, acceleration is positive.

• TRUE

• FALSE

Answer explanation

When velocity is constant there is no acceleration.

A falling object is accelerating.

• TRUE

• FALSE

Acceleration has magnitude as well as direction.

• TRUE

• FALSE

The SI unit of acceleration is m/s².

• TRUE

• FALSE

A falling object has increasing acceleration.

• TRUE

• FALSE

A car accelerates from 20 m/s to 80 m/s in 5 seconds. What is the average acceleration of the car?

• 20 m/s²

• 4 m/s²

• 16 m/s²

• 12 m/s²

A bus approaches red traffic light, and slows down from a speed of 18 m/s to rest in 3 seconds. What is the average acceleration?

• 6 m/s²

• -6 m/s²

• 15 m/s²

• -9 m/s²

A body starts from rest and falls vertically downwards in 2 s. What will be the velocity of the body before striking the ground if acceleration due to gravity, 9.8 m/s².

• 9.8 m/s²

• 4 m/s²

• 0 m/s²

• 19.6 m/s²

A car travels the first 30 km at a uniform speed of 50 km/hr and the next 20 km at a uniform speed of 40 km/hr. What is the average speed of the car?

• 45 km/h

• 45.5 km/h

• 46 km/h

• 46.5 km/h

A bike starts from rest and accelerates to a speed of 15 m/s over the course of 5 seconds. Calculate the average acceleration and enter your answer as a number.