Question

A \[50.0\,{\text{kg}}\] boy is sitting on an amusement park ride where he accelerates straight upward from rest to a speed \[30.0\,{\text{m/s}}\] in \[3.0\,{\text{s}}\]. What is his mass as he accelerates upward?
A. \[990.0\,{\text{kg}}\]
B. \[100.0\,{\text{kg}}\]
C. \[50.0\,{\text{kg}}\]
D. \[5.0\,{\text{kg}}\]
E. \[0\,{\text{kg}}\]

Answer 1

Hint:We know that there are some physical quantities whose value does not change at any place in the universe. Check whether the mass of an object is such physical quantities which is the same throughout the universe or not. If the mass changes with position then determine the mass of the boy as he accelerates upward.

Complete step by step answer:
We have given that a boy of mass \[50.0\,{\text{kg}}\] is sitting on an amusement park ride.
\[m = 50.0\,{\text{kg}}\]
The ride in which the boy is sitting accelerates straight upwards from rest to a speed \[30.0\,{\text{m/s}}\] of in \[3.0\,{\text{s}}\].
\[v = 30.0\,{\text{m/s}}\]
\[\Rightarrow t = 3.0\,{\text{s}}\]
We have asked to calculate the mass of the boy as he accelerates upward.We know that the mass and weight of an object are two different physical quantities.The weight of an object is the product of mass of the object and acceleration due to gravity at the plane where the weight is to be measured.

Hence, the weight of an object is a variable physical quantity which changes with the value of acceleration due to gravity.But the mass of any object is a constant physical quantity. The mass of an object always remains the same at any place in the universe.Hence, although the boy accelerates and goes upwards, the mass of the boy remains the same.Therefore, the mass of the boy as the ride accelerates upward is \[50.0\,{\text{kg}}\].

Hence, the correct option is C.

Note:The students should be clear with the concepts of mass and weight of an object. If one gets confused between these two physical quantities then one may try to determine the value of acceleration due to gravity at the changed position of the boy. But this is a waste of time as mass does not change with change in position.