3.1 understanding pressure
TRANSCRIPT
Pressure :
Pn Haziah bt Awang Lah, Sekolah Sultan Alam Shah. 2007
3.1 UNDERSTANDING PRESSURE
Relationship between pressure and force, pressure and surface area
Situation 1 : Press a thumbtack into a piece of wood with your thumb (figure 3.1a) and then hit using the hammer (figure 3.1b).
Figure 3.1a Figure 3.1b
P
F Situation 2 : A boy tries to pop a balloon by using his finger (figure 3.2a) and then a needle (figure 3.2b).
Figure 3.2a Figure 3.2b
P P
TEACHER’S SIGNATURE : …………………………42
P = F = Force (N)A = surface area (m2)P = Pressure (
(a) Observe figure 3.1a and figure 3.1b and state one comparision.
…………………………………………………
…………………………………………………
(b) Which one is received a higher force?
……………………………………………
(c) State the relationship between pressure and force.
…………………………………………………
A 1/A
(a) Observe figure 3.2a and figure 3.2b. and compare.
………………………………………………
……………………………………………….
(b) Which figure shows that the higher pressure is exerted to the balloon?
…………………………………………..
(c) State the relationship between pressure and surface area.
……………………………………………..
……………………………………………..
Pn Haziah bt Awang Lah, Sekolah Sultan Alam Shah. 2007
Application of pressure in our daily life.
Give one benefit for high pressure and low pressure.
(a) High pressure.
(b) Low pressure
Solving Problem
1. Calculate the pressure on a wall when the palm of a hand with area 150 cm2 is pushed against the wall a force of 210 N.
2. A teacher who weights 637N has a foot with a surface area of 200 cm2. When he stand with one foot, calculate the force applied.
3. Calculate the pressure exerted at the point of drawing pin if pushed against a board with a force of 5 N, assuming the area of the point is 0.1 mm2.
4. A 68 kg is standing in a lawn. Calculate the pressure applied to the soft ground if she is wearing :
(a) flat shoes with a contact area of 160 cm2
(b) high-heeled shoes with total contact area of 54 cm2
TEACHER’S SIGNATURE : …………………………43