Liquid Pressure
- Water exerts a liquid pressure.
- Water molecules are close together . They will collide with each other, the container and
anything in the water.
- Liquid pressure acts in all directions.
- Pressure increases with depth as there are more particles pushing down.
Density
- The denser the liquid, the greater the pressure ecxerted at the same depth. This is due to there
being a greater weight of liquid pushing down in the denser liquid.
Calculating
- Pressure (Pa) = Height of column (m) x Density of liquid (kg/m 3) x Gravitational Field Strength
(N/kg)
- Calculate the pressure at the bottom of aa column of liquid of height 50cm. The density of the
liuid is 1200kg/m3. The gravitational field strength is 10N/kg.
o Pressure = (50/100) x 1200 x 10
o = 6000 Pa
Total Pressure
- The total pressure would be the liquid pressure plus the atmospheric pressure.
Floating
- Items float when the upthrust balances the weight.
Calculations
- Pressure (Pa) = Force (N) / Area (m 2)
- A tanker has a mass of 20 million kilograms. The area in contact with the water is 20,000m 2.
Estimate the depth at which the ship floats. The density of water is 1000kg/m 3 and gravitation
field strength is 10N/kg.
o Calculate weight = Mass x g
o = 20,000,000 x10
o = 200,000,000N
o Pressure = Depth x Density x g
o Force = Pressure x Area
o So Force = Depth x Density x g x Area
o Depth = Weight/ (Density x g x Area)
o 200,000,000 / (1000 x 10 x 20,000)
o 1m
Floating or Sinking
- Submarines are able to float at different depths.
- Their structure has tanks which are either filled with air or water to adjust the depth it floats at.
, P2
Measuring Speed
- Measuring Distance: Ruler
- Measuring Time: Stop watch or light gate
- Ultrasound can also be used to measure distance.
- The device measures the time taken for a pulse to travel to an object and back.
- It then calculate es the distance using speed and time.
Calculating
- In uniform motion, the speed does not change.
- Speed (m/s) = Distance (m) / TIme (s)
- In non-uniform motion, the speed changes.
- WE use:
o Average speed (m/s) = Total Distance (m) / Total Time (s)
- A car moves 100m in 50s. Calculate the speed of the car.
o Speed = Distance / Time
o = 100/50
o 2m/s
Converting Units
- 1 km = 1000m
- 1 mile = 1609m
- 1 hour = 3600s
Vectors and Scalars
- Vector: A quantity that has a direction and a magnitude (size).
o E.g. forces
o Represented with an arrow where the length shows magnitude and the direction shows
direction.
- Scalar: A quantity that has a magnitude (size) but no direction.
o E.g. time
Distance and Displacement
- Distance: How far you have travelled. (Scalar)
- DisplacementL Distance from a point in a particular direction. (Vector) Can be written as 2 miles
east or +2 miles.
Speed and Velocity
- Speed: How fast an object travels. (Scalar)
- Velocity: How fast something travels in a given direction. (Vector)
- You can assign positive values to a certain direction.
- Water exerts a liquid pressure.
- Water molecules are close together . They will collide with each other, the container and
anything in the water.
- Liquid pressure acts in all directions.
- Pressure increases with depth as there are more particles pushing down.
Density
- The denser the liquid, the greater the pressure ecxerted at the same depth. This is due to there
being a greater weight of liquid pushing down in the denser liquid.
Calculating
- Pressure (Pa) = Height of column (m) x Density of liquid (kg/m 3) x Gravitational Field Strength
(N/kg)
- Calculate the pressure at the bottom of aa column of liquid of height 50cm. The density of the
liuid is 1200kg/m3. The gravitational field strength is 10N/kg.
o Pressure = (50/100) x 1200 x 10
o = 6000 Pa
Total Pressure
- The total pressure would be the liquid pressure plus the atmospheric pressure.
Floating
- Items float when the upthrust balances the weight.
Calculations
- Pressure (Pa) = Force (N) / Area (m 2)
- A tanker has a mass of 20 million kilograms. The area in contact with the water is 20,000m 2.
Estimate the depth at which the ship floats. The density of water is 1000kg/m 3 and gravitation
field strength is 10N/kg.
o Calculate weight = Mass x g
o = 20,000,000 x10
o = 200,000,000N
o Pressure = Depth x Density x g
o Force = Pressure x Area
o So Force = Depth x Density x g x Area
o Depth = Weight/ (Density x g x Area)
o 200,000,000 / (1000 x 10 x 20,000)
o 1m
Floating or Sinking
- Submarines are able to float at different depths.
- Their structure has tanks which are either filled with air or water to adjust the depth it floats at.
, P2
Measuring Speed
- Measuring Distance: Ruler
- Measuring Time: Stop watch or light gate
- Ultrasound can also be used to measure distance.
- The device measures the time taken for a pulse to travel to an object and back.
- It then calculate es the distance using speed and time.
Calculating
- In uniform motion, the speed does not change.
- Speed (m/s) = Distance (m) / TIme (s)
- In non-uniform motion, the speed changes.
- WE use:
o Average speed (m/s) = Total Distance (m) / Total Time (s)
- A car moves 100m in 50s. Calculate the speed of the car.
o Speed = Distance / Time
o = 100/50
o 2m/s
Converting Units
- 1 km = 1000m
- 1 mile = 1609m
- 1 hour = 3600s
Vectors and Scalars
- Vector: A quantity that has a direction and a magnitude (size).
o E.g. forces
o Represented with an arrow where the length shows magnitude and the direction shows
direction.
- Scalar: A quantity that has a magnitude (size) but no direction.
o E.g. time
Distance and Displacement
- Distance: How far you have travelled. (Scalar)
- DisplacementL Distance from a point in a particular direction. (Vector) Can be written as 2 miles
east or +2 miles.
Speed and Velocity
- Speed: How fast an object travels. (Scalar)
- Velocity: How fast something travels in a given direction. (Vector)
- You can assign positive values to a certain direction.
