- #1
brad sue
- 281
- 0
Hi, Please , take a look at this problem:
A child is trying to shoot a marble of mass m in order to hit the center of a box using a spring loaded marble gun.
The marble gun is fixed on a table and shoots the marble horizontally from the edge of the table. The edge of the table is a height h above the top of the box. The center of the box is some horizontal distance d away from the table. the spring constant is k. By what distance x should the child compress the spring so that the marble lands in the center of the box?. g is the gravitational constant.
In the solution , the manual used the conservation of mechanical energy.( I got this part).
My problem is that I don't understand why they did not use the potential energy PE=mgh
They wrote Eo=1/2*k*x2=1/2*m*v12=E1
They solved for v1, and the they used the projectile equation to find x ( by finding t)
My problem is why for the conservation of energy, they did not write:
Eo=mgh+1/2*k*x2
I saw that in other problems solutions tough!
Thank you
A child is trying to shoot a marble of mass m in order to hit the center of a box using a spring loaded marble gun.
The marble gun is fixed on a table and shoots the marble horizontally from the edge of the table. The edge of the table is a height h above the top of the box. The center of the box is some horizontal distance d away from the table. the spring constant is k. By what distance x should the child compress the spring so that the marble lands in the center of the box?. g is the gravitational constant.
In the solution , the manual used the conservation of mechanical energy.( I got this part).
My problem is that I don't understand why they did not use the potential energy PE=mgh
They wrote Eo=1/2*k*x2=1/2*m*v12=E1
They solved for v1, and the they used the projectile equation to find x ( by finding t)
My problem is why for the conservation of energy, they did not write:
Eo=mgh+1/2*k*x2
I saw that in other problems solutions tough!
Thank you