A man of mass $80kg$ carrying a load of $20kg$ walks up a stair case in $20s$. If the number of steps is $40$ and width and height of each step are $20cm$ and $15cm$ respectively. The efficiency of the man is
A man uses a crowbar of length $1.5m$ to raise a load of $75kgf$ by putting a sharp edge below the bar at a distance $1m$ from his hand. Calculate the mechanical advantage.
A water -pump driven by petrol raises water at a rate $ 0.5 m^3/min $ from a depth of 30 m. if the pump is 70% efficient, what power is developed by the engine?
A $20\ N$ metal block is suspended by a spring balance. A beaker containing some water is placed on a weighing machine which reads $40\ N$. The spring balance is now lowered so that the block gets immersed in the water. The spring balance now reads $16\ N$. The reading of the weighing machine will be
A man uses a crowbar of length $1.5m$ to raise a load of $75kgf$ by putting a sharp edge below the bar at a distance $1m$ from his hand. Calculate the effort needed.
A boy can exert a maximum effort of $250\ N$, so he uses an inclined plane to lift the load up. What should be the minimum length of the plank used by him to lift a mass of $ 50 \ kg$ to a height of $1 \ m$ ?
A coolie uses a sloping wooden plank of length $2.0 m$ to push up a drum of mass $100 kg$ into the truck at a height $1.0 m$. What is the mechanical advantage of the sloping plank ?
A fire tongs has its arms $20cm$ long. It is used to lift a coal of weight $1.5kgf$ by applying an effort at a distance $15cm$ from the fulcrum. Find the mechanical advantage of fire tongs.
A fire tongs has its arms $20 \ cm$ long. It is used to lift a coal of weight $1.5 \ kgf$ by applying an effort at a distance $15 \ cm$ from the fulcrum. Find the effort needed.
It is harder to cut an apple with a butter-knife, because: