Question

The passengers are thrown outwards when a bus suddenly takes a turn. This happens because of
A. inertia of motion
B. acceleration of motion
C. speed of motion
D. Both (b) and (c)

Answer 1

Hint: You can think of the property that may be responsible for this action. You could consider each of the given options as a possible answer and hence find the correct answer with clear justification. Also, recall Newton’s first law of motion and then answer.

Complete answer:
In the question we are given a bus that suddenly takes a turn and as a result of that the passengers are thrown outwards. We are asked to find the reason behind the passengers being thrown outwards.
You may have encountered this situation in your day to day life. So, let us understand the physics behind this.
You may be familiar with Newton’s first law of motion which is otherwise called law of inertia. This law states that, ‘Every body continues to be in its state of rest or of uniform motion in a straight line unless compelled by some external force.’ Newton’s first law basically defines the property of the body called inertia. Inertia of a body is the property by which resists change in its state of rest or uniform motion in the absence of application of an external force.
We have three types of inertia:
(1) Inertia of rest: Here the body continues to be in its state of rest in the absence of external force.
(2) Inertia of motion: Here the body continues to be in its state of motion in the absence of external force.
(3) Inertia of direction: Here the body continues to remain in the same direction in the absence of external force.
It is this third type of inertia that causes the passengers to be thrown outwards when the driver makes a sudden turn. When the driver takes a sudden turn, the body tends to continue in the same direction as before and hence gets thrown to the side.

So, the correct answer is “Option A”.

Note:
For a standing passenger in a bus, if the driver starts the bus suddenly, he falls backwards with a jerk due to inertia of rest. Also, when a uniformly moving bus stops suddenly, he gets thrown forward due to inertia of motion. In both the above cases, the net force acting on the body is zero.