Advertisements
Advertisements
Question
What is a lever?
Solution
A lever is a special case of the application of the law of moments. It is a rigid bar, straight or bent, which is capable of rotation about a fixed point or a fixed-line, called the axis of rotation. This fixed point or the axis of rotation is called the fulcrum. An effort E is applied at point A of the lever to overcome resistance (or load) at another point B, as shown in the diagram.
APPEARS IN
RELATED QUESTIONS
Give one example of a class I lever where mechanical advantage is more than one ?
shows a nut cracker name the class of lever ?
A 4 m long rod of negligible weight is to be balanced about a point 125 cm from one end and a load of 18 kgf is suspended at a point 60 cm from the support on the shorter arm.
- If a weight W is placed at a distance of 250 cm from the support on the longer arm to balance the rod, find W.
- If a weight 5 kgf is kept to balance the rod, find its position.
- To which class of lever does it belong?
A man uses a crowbar of length 1.5 m to raise a load of 75 kgf by putting a sharp edge below the bar at a distance 1 m from his hand.
- Draw a diagram of the arrangement showing the fulcrum (F), load (L) and effort (E) with their directions.
- State the kind of lever.
- Calculate:
- load arm,
- effort arm,
- mechanical advantage and
- the effort needed.
A lever of length 9 cm has its load arm 5 cm long and the effort arm is 9 cm long.
- To which class does it belong?
- Draw a diagram of the lever showing the position of fulcrum F and directions of both the load L and effort E.
- What is the mechanical advantage and velocity ratio if the efficiency is 100%?
- What will be the mechanical advantage and velocity ratio if the efficiency becomes 50%?
The following belong to which class of lever?
A claw-hammer
The following belong to which class of lever?
A fire tongs
The following belong to which class of lever?
A pair of scissors
Shears, used for cutting metals and scissors used for cutting clothes are both examples of levers of the first order. However, whereas the shears always have short blades and long handles, the scissors often have blades much longer than the handles. Explain, why this is so?
The length of a nut-cracker is 12 cm. A nut, when kept at a distance of 4 cm from its fulcrum, requires an effort of 100 gf to crack it. What force will be required to crack the nut without using the nut-cracker?