Question

Give scientific reasons: why the weight of an object at the equator is less than at the poles?

Answer 1

The weight of an object at the equator is less than at the poles due to the following reason:

• The value of acceleration due to gravity, 'g' is greater at poles as compared to its value at the equator.
• It is because the earth is not perfectly spherical. The radius of the equator is slightly greater than the radius of the poles.    
• Since, weight of the object, w = mg, so weight of an object at the equator is slightly less than at the poles. (keeping the mass, 'm' as constant)

Answer 2

There are 2 resons for which the weight at equator is less that of poles :

1. Rotation of the earth:

The general equation for gravitational acceleration at various latitudes can be given as:

$\boxed{ \bf g = g_{0} - r { \omega}^{2} \cos( \lambda) }$

• r is radius of earth , $\omega$ is angular velocity of earth and $\lambda$ is angle of latitude.

Now, at equator , value of $\lambda$ =0°, but at poles $\lambda$= 90° , so we can say:

$\boxed{ \bf g_{poles} = g_{0} }$

$\boxed{ \bf g_{equator}= g_{0} - r { \omega}^{2} }$

• Since the gravitational acceleration at the equator is less than that of the poles an object will have lesser weight at the equator.

This is the actual reason expected from class 11-12 students.

2. Spheroidal shape of earth:

• The it is not completely spherical and the radius at the equator is slightly greater as compared to that of the poles.

• That is why , the gravitational acceleration at the equator is slightly less as compared to that of the poles.

• And hence the weight is lesser at the poles.