Questions on Pressure
Q8. The drawing shows an elfin archer. She is holding an arrow and pulling the string of the bow back.
(a) Two horizontal forces act on the arrow.
These are the force exerted by the elf's hand and the force exerted by the string.
The arrow is not moving. The elf pulls the arrow with a force of 150 N.
What is the size of the force exerted by the string on the arrow?
150 
N
(2 marks)
(b) When the elf lets go of the arrow, it starts to move forward.
Explain why it starts to move.
There is no longer a force to balance the force of the string so the arrow is pushed by the string.
The potential energy stored in the bow is converted to kinetic energy in the arrow.
(1 mark)
(c) The arrow flies across a field and hits an orc.
Two forces act on the arrow while it is in the air.
Air resistance acts in the opposite direction to the movement, and gravity acts downwards.
These two forces cannot balance each other, even when they are the same size.
Why is this?
any one from
because they are not acting in opposite directions
because they do not act along the same line of action - gravity pulls down and friction pushes across
( 1 mark)
(d) The arrow has a sharp pointed end. When the arrow hits the orc, the sharp point exerts a very large pressure on him.
Why does a sharp pointed end exert a larger pressure than a blunt end?
Because pressure is force divided by contact area and if the area of contact is small the pressure will be larger.
(2 marks)
Maximum 6 marks
About this site
