Question

Please help

Imagine making a heavy door swing open by giving it a brief hard push. First, you push at its center, "push I " in the diagram Then you push near the edge, "push 2." Both pushes are equally hard akd last the same time. Which push is more effective at making the door swing open? Why? Again, let’s compare the effectiveness of two pushes. This time, both pushes are applied to the same spot on the door. But push A is two times stronger than push 3. Which push, 3 or 4, is more effective at making the door swing open? How much more effective? Explain. A half-meter stick is balanced on a pivot, as shown here. Wc can hang weights along the meter stick to affect its balance. Predict whether the following arrangements of washers will balance. Circle the scenarios that will balance. In the arrangement below, where could you add a single washer to make the beam balance?

Answer 1

1)

Push 2 is more effective as the torque produced by the push is more in this case than the other

2)

Push 4 is more effective as the torque produced is 2 times the torque produced in Push 3

3)

Let the mass of each hanging mass be m

For the arrangement 1) (top-left one)

So, torque produced by the mass on the left, Tl = m*4d

Torque produced by the mass on the left,Tr = m*2d

As the two torques are not same . So they wont balance

For arrangement 2) (top-right)

Torque produced by the mass on left,Tl = m*4d = 4md

for the masses on the right,Tr = 2m*2d = 4md

As the torques are same, so they will balance out <------- balanced

For arrangement 3) (bottom left)

Tl = 3m*0.5d = 1.5*md

Tr = m*1.5d = 1.5md

So, it will balance out

Arrangement, 4)

Tl = 2m*4.5d = 9md

Tr = m*1.5d + m*2d +m*2.5d + m*3d = m*d*(1.5+2.5+2+3) = md*(4+5) = 9md

So, It will also balance .

B)

Here Tl = m*d + m*3.5*d = 4.5md

Tr = 3m*3d = 9md

So, the distance required = (9md - 4.5md)/(m) = 4.5*d