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A man uses a crowbar of length 1.5 m to raise a load of 75kgf by putting a sharp edge below the bar at a distance 1 m from his hand. (a) Draw a diagram of the arrangement showing the fulcrum (F), load (L) and effort (E) with their directions. (b) State the kind of lever. (c) Calculate: (i) load arm, (ii) effort arm, (iii) mechanical advantage, and (iv) the effort needed.
A man uses a crowbar of length 1.5 m to raise a load of 75kgf by putting a sharp edge below the bar at a distance 1 m from his hand. (a) Draw a diagram of the arrangement showing the fulcrum (F), load (L) and effort (E) with their directions. (b) State the kind of lever. (c) Calculate: (i) load arm, (ii) effort arm, (iii) mechanical advantage, and (iv) the effort needed.
Class 10 | ICSE | Machines | Physics | Selina
A man uses a crowbar of length 1.5 m to raise a load of 75kgf by putting a sharp edge below the bar at a distance 1 m from his hand. (a) Draw a diagram of the arrangement showing the fulcrum (F), load (L) and effort (E) with their directions. (b) State the kind of lever. (c) Calculate: (i) load arm, (ii) effort arm, (iii) mechanical advantage, and (iv) the effort needed.

Solutions:

As evident form the diagram, crowbar is a class I lever.

According to the question –

(i) Total length of crowbar is 1.5 m

Effort arm is 1 m long

Load arm then becomes 1.5 – 1 = 0.5 m long

(ii) Effort arm is 1 m

(iii) Expression for Mechanical advantage is –

M.A. = Effort arm / Load arm = 1 / 0.5

M.A. = 2

(iv) The effort needed can be calculate using the expression below –

Effort = Load / M.A. = 75 / 2

Effort = 37.5 kgf

i

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