Physics Form 4 Chapter 3
Discuss your physics questions online at www.physics4spm.com
3 FORCES AND PRESSURE
3.1 UNDERSTANDING PRESSURE Pressure is force per unit area Pressure = Force Area
P= F A
1. Define Pressure 2. State pressure’s formula
3. State relationship between pressure and area. 4. Describe applications involving High Pressure Increasing the pressure by reducing the area A sharp knife has a very The studs on a football small surface area on its boot have only a small cutting edge so that high area of contact with the pressure can be exerted ground. The pressure to cut the meat. under the studs is high enough for them to sink into the ground, which gives extra grip.
The SI unit : Nm-2 = Pascal = Pa The pressure of a given force increases as the surface area decreases.
Nails, needles and pins have very sharp ends with very small surface areas. When a force is applied to the head of a nail, the pressure will drive its sharp end into a piece of wood easily.
The sole of an ice is fixed a narrow metal bar. The high pressure on surface of the ice so that the ice melts and allowing the ice skater to glide smoothly .
Racing bicycles need very high air pressure inside the tyres, because the narrow tyres have a very small contact area with the road. The hard road surface can support the high pressure under the wheels.
37
www.physics4spm.com
Discuss your physics questions online at www.physics4spm.com
5. Application involving Low Pressure Reducing the pressure by increasing the area Skis have a large area to A tractor moving on soft ground has wide reduce the pressure on the snow so that they do tires to reduce the pressure on the not sink in too far. ground so that they will not sink into the ground.
A wide shoulder pad of a heavy bag will reduce the pressure exerted on the shoulder of the person carrying the bag.
Example 1 A block of metal of dimensions 0.5 m x 0.6 m x 1.0 m has a mass of 300 kg. Calculate the maximum pressure acting on the ground.
A student pressing a
3 FORCES AND PRESSURE
3.1 UNDERSTANDING PRESSURE Pressure is force per unit area Pressure = Force Area
P= F A
1. Define Pressure 2. State pressure’s formula
3. State relationship between pressure and area. 4. Describe applications involving High Pressure Increasing the pressure by reducing the area A sharp knife has a very The studs on a football small surface area on its boot have only a small cutting edge so that high area of contact with the pressure can be exerted ground. The pressure to cut the meat. under the studs is high enough for them to sink into the ground, which gives extra grip.
The SI unit : Nm-2 = Pascal = Pa The pressure of a given force increases as the surface area decreases.
Nails, needles and pins have very sharp ends with very small surface areas. When a force is applied to the head of a nail, the pressure will drive its sharp end into a piece of wood easily.
The sole of an ice is fixed a narrow metal bar. The high pressure on surface of the ice so that the ice melts and allowing the ice skater to glide smoothly .
Racing bicycles need very high air pressure inside the tyres, because the narrow tyres have a very small contact area with the road. The hard road surface can support the high pressure under the wheels.
37
www.physics4spm.com
Discuss your physics questions online at www.physics4spm.com
5. Application involving Low Pressure Reducing the pressure by increasing the area Skis have a large area to A tractor moving on soft ground has wide reduce the pressure on the snow so that they do tires to reduce the pressure on the not sink in too far. ground so that they will not sink into the ground.
A wide shoulder pad of a heavy bag will reduce the pressure exerted on the shoulder of the person carrying the bag.
Example 1 A block of metal of dimensions 0.5 m x 0.6 m x 1.0 m has a mass of 300 kg. Calculate the maximum pressure acting on the ground.
A student pressing a