Question

If you try opening a door by pushing too close to the side where the hinges are, you may find it difficult to push open. Suppose you are trying to open a door that is 75 cm wide. (Hint: To solve this one, remember the example problem in the lesson about the MA of the broom). a. If you push on the door at a point 15 cm away from the hinges, what is the mechanical advantage? b. What is the best mechanical advantage that you can obtain for any door that you simply push open? Your answer:

Answer 1

Answer:

a) Mechanical advantage is 0.2

b) maximum obtainable mechanical advantage is 1

Explanation:

The opening of the door is only possible when a force is used to push the door, by generating a torque on the door around the hinge.

Since the door is 75 cm wide, torque generated will be the product of the force applied and the width of the door.

torque = F x 75 = 75F

If the door was pushed at point on the door 15 cm from the hinges, the torque that will be generated will be

torque = F x 15 = 15F

a)The mechanical advantage MA is therefore

MA = 15/75 = 0.2

b) The best mechanical advantage that can be obtained from when you simply push it open is 1

From the case above, if we assume we push it at its maximum width from the hinge, then

MA = 75/75 = 1