Page 86 - Physics Form 5 KSSM_Neat

Solving Problems Involving Archimedes' Principle and Buoyancy
When an object is in a fluid:

Buoyant force = weight of fluid displaced
F = ρVg
B
KEMENTERIAN PENDIDIKAN MALAYSIA
When an object is floating in a fluid:

Buoyant force = weight of object
LET’S ANSWER
= weight of fluid displaced LET’S ANSWER

Example 1

Figure 2.41 shows a line L on a boat. The volume of http://bit.ly/
the boat below the line L is 2.8 m . The mass of the Line L 35JwZyh
3
boat is 600 kg. What is the weight of the maximum
load that can be carried by the boat?
[Density of water, ρ = 1 000 kg m and
–3
gravitational acceleration, g = 9.81 m s ]
–2
Figure 2.41
Solution

Step 1: Step 2: Step 3: Step 4:
Identify the Identify the Identify the formula Solve the problem
problem information given that can be used numerically

 Let the weight of maximum load that can 3 Weight of boat, W = mg
be carried = B W + B = buoyant force
= weight of water displaced
2 Volume of boat below line L = 2.8 m 3 = ρVg
When the boat floats with a depth of
immersion at line L, volume of water
displaced, V = 2.8 m 3  W = 600 × 9.81
Density of water, ρ = 1 000 kg m –3 = 5 886 N
Gravitational acceleration, g = 9.81 m s –2 5 886 + B = 1 000 × 2.8 × 9.81
Mass of boat, m = 600 kg B = 27 468 – 5 886
= 21 582 N

76 LS 2.5.4