Which of the following is not a vector quantity?

A. Weight
B. Nuclear spin
C. Momentum
D. Potential energy

Hint: Approach the problem by analyzing each option. Discard any option which is not true. Vector quantities have a magnitude and direction. So, if the quantity does not have direction, then the quantity is not a vector quantity.

Complete step by step answer:
First, let us consider the quantity in option (A). Weight is a vector quantity because it has a direction and it works along the direction of gravitational acceleration. Weight of an object is given by,
$W=mg$
Where, m is the mass of the object, and g is the gravitational acceleration.
As acceleration is a vector quantity, weight is also a vector quantity.
Now, Nuclear spin has a direction as well. You can determine the direction of the vector using the right-hand rule. If you curl your fingers according to the spin, your thumb will point towards the direction of the vector. As a result, Nuclear spin is also a vector quantity.
Thirdly, momentum is a vector quantity as well. The momentum of an object is given by,
$p=mv$
Where, m is the mass of the object, and v is the velocity of the object. As it is a product of a scalar quantity and a vector quantity, momentum is also a vector quantity.
Lastly, potential energy is not a vector quantity because it does not have a direction. Energy does not have a direction, and it is a scalar quantity. Hence, potential energy is the correct choice.

The correct answer is (D).

Note:Potential energy is the energy a particle has because of its position in a system. There can be various types of potential energy. The most common definition of the potential energy is the following, The energy required to bring an object from infinite distance to a point inside a system. The system can be electrical, magnetic, or gravitational.