1) When you rise from a chair, you have to lean quite far forward (try it!). Why

Question

1) When you rise from a chair, you have to lean quite far forward (try it!). Why is this?

2) The two ends of the dumbbell shown in the figure are made of the same material.Is the dumbbell's center of gravity at point 1, 2, or 3? Explain.

3) A common type of door stop is a wedge made of rubber. Is such a stop more effective when jammed under the door near or far from the hinges? Why?

4) A screwdriver with a very thick handle requires less force to operate than one with a very skinny handle. Explain why this is so.

When you rise from a chair, you have to lean quite far forward (try it!). Why is this? The two ends of the dumbbell shown in the figure are made of the same material. Is the dumbbell's center of gravity at point 1, 2, or 3? Explain. A common type of door stop is a wedge made of rubber. Is such a stop more effective when jammed under the door near or far from the hinges? Why? A screwdriver with a very thick handle requires less force to operate than one with a very skinny handle.

Explanation / Answer

1 ) You have to get your centre of gravity to be over the vertical line from your feet, in order to be able to stand.

2) center of gravity lies at 1 because center of gravity is closer to the heavier region. product of mass and distance is constant

3)2 At the greatest distance from the hinge. Reason as below, torque around hinge as centre of rotation

4) A larger radius of the handle allows more torque on the front end of the screw driver, because the force is applied at a greater moment arm than with a thinner handle .

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