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Which of the following three statements used to describe work are true:
i)Work is done only if an object moves through a distance
ii)Work is done only if energy is transferred from one form to another
iii)Work is done only if a force is applied

In which of the following situations does an object have both kinetic and potential energy?
a)A plane is flying at the height of 3 km
b)A rock is perched at the top of a cliff
c)A puck slides across the ice
d)A book rests on a shelf

Make a statement about the IMA of pliers.

I'm guessing 1 is I,II and III
2 is a)
and I'm stuck on 3

Thanks!

1) To determine which statements about work are true, let's analyze each statement:

i) "Work is done only if an object moves through a distance."
This statement is true. In order for work to be done, an object must be displaced in the direction of the applied force.

ii) "Work is done only if energy is transferred from one form to another."
This statement is not necessarily true. Energy transfer can occur without work being done. For example, if you hold a heavy object steady, no work is done even though energy may be transferred due to the object's gravitational potential energy.

iii) "Work is done only if a force is applied."
This statement is true. Work is defined as the product of the force applied on an object and the distance over which the force is exerted.

Therefore, the correct answer is i) and iii) - "Work is done only if an object moves through a distance" and "Work is done only if a force is applied."

2) To determine which situation involves an object having both kinetic and potential energy, let's analyze each option:

a) "A plane is flying at the height of 3 km."
In this situation, the plane has both kinetic and potential energy. The plane's height above the ground represents potential energy, while its motion through the air represents kinetic energy. Therefore, option a) is correct.

b) "A rock is perched at the top of a cliff."
In this situation, the rock has potential energy due to its position, but it does not have kinetic energy since it is not in motion. Therefore, option b) is incorrect.

c) "A puck slides across the ice."
In this situation, the puck has only kinetic energy as it moves over the ice. It does not have potential energy since it is not at a height or in a position that would give it potential energy. Therefore, option c) is incorrect.

d) "A book rests on a shelf."
In this situation, the book does not have any kinetic or potential energy. It is at rest, so it does not possess kinetic energy, and it is not at a height or in a position that would give it potential energy. Therefore, option d) is incorrect.

Therefore, the correct answer is a) - "A plane is flying at the height of 3 km."

3) In order to make a statement about the Ideal Mechanical Advantage (IMA) of pliers, we need more specific information about the pliers and their mechanical properties. IMA is a measure of how much the force applied to a machine is amplified. It is calculated by dividing the effort distance (the distance over which the exerted force is applied) by the load distance (the distance over which the output force is exerted). Please provide additional details about the specific pliers you are referring to, such as their design or any measurements, so that I can assist you further.