Gravitational potential energy, relative to some level =
(mass of the object)
times
(height above the reference level)
times
(acceleration due to gravity) .
At 1 because the cart is still at the top
Answer:
Li has less mass and therefore less inertia, so he can change his motion more easily than Raj.
Explanation:
Inertia describes the resistance of an object to any change in its state of motion, and it depends on the mass of the object only. In particular:
- if an object has a large inertia (large mass), then it is more difficult to change its state of motion (i.e. to put it in motion, or to slow it down, or to change its direction of motion)
- if an object has small inertia (small mass), then it is more easy to change its state of motion
In this problem, Li has less mass than Raj, so he has less inertia, therefore he can change his motion more easily than Raj.
By looking at the acceleration of the object.
In fact, Netwon's second law states that the resultant of the forces acting on an object is equal to the product between the mass m of the object and its acceleration:

So, when static friction is acting on the object, if the object is still not moving we know that all the forces are balanced: in fact, since the object is stationary, its acceleration is zero, and so the resultant of the forces (left term in the formula) must be zero as well (i.e. the forces are balanced).