Physics Lab worksheet on Archimedes upthrust. An example of a physics Lab worksheet, based on guided discovery approach.

1. Page 1 of 7
Physics Lab
worksheet# 11 Archimedes’ upthrust
Name: Teacher: Farid Minawi
Experiment 1
Existence of upthrust force in liquids
Materials:
- A wooden rectangular or square block.
- A metallic rectangular or square block.
- A beaker containing water.
Procedure:
1.1. Immerse the woodent block in water, then release it. Does it sink or float?
…………………………………………………………………………………………………………………………………
1.2. Immerse metallic block in water, then release it. Does the object sink or float?
…………………………………………………………………………………………………………………………………
1.3. What is forcing the floating object to go up?
………………………………………………………………………………………………...........................................................................
1.4. Can we conclude that there is a push force exerted by the liquid? What is the direction of this
force?
………………………………………………………………………………………………...........................................................................
1.5. From this experiment, we conclude that: (choose the correct statement or statements)
[ ] In a certain liquid, some objects sink and some float.
[ ] A liquid exerts on objects within it a thrust (push) force downwards, then we call this force
down-thrust.
[ ] A liquid exerts on objects within it a thrust (push) force upwards, then we call this force up-
thrust.

2. Page 2 of 7
Experiment 2
Floating and sinking
Materials:
Same as in experiment 1, plus a digital balance and a graduated cylinder.
Procedure:
2.1. Measure the mass of the graduated cylinder using a digital balance.
………………………………………………………………………………………......................................................................................
2.2. Pour some of the water used in experiment 1 into the graduated cylinder and read the volume
of water in the cylinder.
………………………………………………………………………………………......................................................................................
2.3. Measure the mass of the graduated cylinder plus the water inside it.
………………………………………………………………………………………......................................................................................
2.4. Deduce the mass of the water inside the graduated cylinder.
………………………………………………………………………………………......................................................................................
2.5. Calculate the density of water (𝑑𝑒𝑛𝑠𝑖𝑡𝑦 =
𝑚𝑎𝑠𝑠
𝑣𝑜𝑙𝑢𝑚𝑒
).
………………………………………………………………………………………......................................................................................
2.6. Measure the dimenstions of the wooden block and calculate its volume.
………………………………………………………………………………………......................................................................................
………………………………………………………………………………………......................................................................................
2.7. Measure the mass of the wooden block using the digital balance.
………………………………………………………………………………………......................................................................................
2.8. Calculate the density of the wooden block.
………………………………………………………………………………………......................................................................................
2.9. Compare the density of the wooden block to the density of water.
………………………………………………………………………………………......................................................................................
2.10. Measure the dimenstions of the metallic block and calculate its volume.

3. Page 3 of 7
………………………………………………………………………………………......................................................................................
………………………………………………………………………………………......................................................................................
2.11. Measure the mass of the metallic block using the digital balance.
………………………………………………………………………………………......................................................................................
2.12. Calculate the density of the metallic block.
………………………………………………………………………………………......................................................................................
2.13. Compare the density of the metallic block to the density of water.
………………………………………………………………………………………......................................................................................
2.14. Can you conclude a condition for the object to float on the surface of a liquid?
………………………………………………………………………………………......................................................................................
2.15. Can you conclude a condition for the object to sink in a liquid?
………………………………………………………………………………………......................................................................................
- You can repeat this experiment with blocks of other substances and different liquid and bolster
your conclusion.
2.16. From this experiment, we conclude that: (choose the correct statement or statements)
[ ] A body floats on the surface of a liquid if its density is greater than the density of the liquid
[ ] A body floats on the surface of a liquid if its density is less than the density of the liquid
[ ] A body sinks in a liquid if its density is less than the density of the liquid
[ ] A body sinks in a liquid if its density is greater than the density of the liquid
Experiment 3
Real weight and apparent weight
Materials:
- An object that sinks in water
- A dynamometer (spring balance)
- A beaker containing liquid.

4. Page 4 of 7
Procedure:
Remark: remember that the dynamometer reads the value of the tension of the spring in
the dynamometer.
3.1. Hang the object from the free end of the dynamometer. Read the indication of the
dynamometer.
………………………………………………………………………………………......................................................................................
3.2. Knowing that this reading represents the tension in spring, and the object is at equilibrium, can
we say that this reading (the tension in the spring) is equal to the weight of the object? Justify.
………………………………………………………………………………………......................................................................................
………………………………………………………………………………………......................................................................................
2.3. Now keep the object hanging from the free end of the dynamometer and
immerse it in a liquid as shown in the adjacent figure. Read the indication of the
dynamometer. We denote this measurement by Wa, the apparent weight of the
object, since it does not represent the real weight of the object.
……………………………………………………………………………………….........................................
3.4. Compare the apparent weight to the real weight.
………………………………………………………………………………………............................................
3.5. The tension in the spring in the first case when the object was not immersed in the liquid is
denoted by T1, and the tension in the spring in the second case when the object was immersed in
the liquid is denoted by T2. In the first case we concluded that the tension in the spring T1 is equal to
the real weight of the object Wr. But in the second case, the tension T2 (which is upward) is less than
the real weight (which is downward). (a) Can we conclude that there must be a third force F
exerted by the liquid in order for the object to be in equilibrium? (b) What must be the direction of
this force? (c) What must be the relation between the magnitudes of these three forces? (d) Justify
your answer. (e) What do we call this force?
………………………………………………………………………………………......................................................................................
………………………………………………………………………………………......................................................................................
………………………………………………………………………………………......................................................................................
………………………………………………………………………………………......................................................................................
………………………………………………………………………………………......................................................................................
………………………………………………………………………………………......................................................................................

5. Page 5 of 7
3.6. From this experiment, we conclude that: (choose the correct statement or statements)
[ ] Real weight = upthrust – apparent weight (Wr = F – Wa)
[ ] Upthrust = real weight – apparent weight (F = Wr – Wa)
[ ] Real weight = apparent weight + upthrust (Wr = Wa +F)
Experiment 4
Displaced liquid
Materials:
- An object that sinks in water
- A dynamometer (spring balance)
- A beaker with a tap
- A small beaker (to collect the overflowing liquid).
- Digital balance
Procedure:
4.1. Measure the real weight of the object in air (Wr)
………………………………………………………………………………………......................................................................................
- Fill the beaker with liquid to the level of the tap.
4.2. Measure the weight of the empty small beaker using the digital balance.
………………………………………………………………………………………......................................................................................
4.3. Put the small beacker under the tap to collect the overflowing liquid and
measure the apparent weight of the object in the liquid (Wa) as shown in the
adjacent figure.
………………………………………………………………………………………................................................
4.4. Calculate Wr – Wa.
………………………………………………………………………………………................................................
4.5. Measure the weight of the displaced liquid (Wl) by measuring the weight of the small beaker
with the displaced liquid in it using the digital balance and then subtracting the weight of the empty
small.

6. Page 6 of 7
………………………………………………………………………………………......................................................................................
4.6. Compare Wl to (Wr – Wa).
………………………………………………………………………………………......................................................................................
4.7. Knowing that F = Wr – Wa, conclude the relation between the upthrust and the weight of the
displaced liquid.
………………………………………………………………………………………......................................................................................
4.8. From this experiment, we conclude that: (choose the correct statement or statements)
[ ] The weight of the displaced liquid is equal to difference between the real weight and apparent
weight (Wl = Wr – Wa)
[ ] The weight of the displaced liquid is equal to the weight of the beaker.
[ ] The weight of the displaced liquid is equal to the upthrust (Wl = F)
Analysis
Floating and sinking
- In this analysis, we are going to derive the result of experiment 2 mathematically.
- Remember the relation between density ρ of an object, its mass m and its volume:
𝜌 =
𝑚
𝑉
⇒ 𝑚 = 𝜌 × 𝑉
- So the weight Wo of the object:
𝑊𝑜 = 𝑚 𝑜 × 𝑔 = 𝜌 𝑜 × 𝑉𝑜 × 𝑔
Where mo is the mass of the object, o the density of the object and Vo the volume of the object.
- Also, the upthrust is equal to the weight of the displaced liquid:
𝐹 = 𝑊𝑙 = 𝑚𝑙 × 𝑔 = 𝜌𝑙 × 𝑉𝑙 × 𝑔
Where ml is the mass of the displaced liquid, l the density of the liquid and Vl the volume of the
displaced liquid.
- Also notice that the volume of the displaced liquid Vl is equal to the total volume of the object Vo
when the object is totally immersed, and is equal to the volume of the immersed part Vi of the object
when the object is partially immersed.

7. Page 7 of 7
Floating on the surface of
the liquid
Floating within the liquid Sinking
 At equilibrium: F = Wo  At equilibrium: F = Wo  Not at equilibrium: F < Wo
Note: Partially immersed
 Vl = Vi
Note: Totally immersed
 Vl = Vo
Note: Totally immersed
 Vl = Vo
F = Wo
ρl × Vl × g = ρo × Vo × g
 ρl × Vl = ρo × Vo
But Vl = Vi
 ρl × Vi = ρo × Vo
But since Vi < Vo then:
ρl > ρo
F = Wo
ρl × Vl × g = ρo × Vo× g
 ρl × Vl = ρo × Vo
But since Vl = Vo then:
ρl × Vo = ρo × Vo
 ρl = ρo
F < Wo
ρl × Vl × g < ρo × Vo× g
 ρl × Vl < ρo × Vo
But since Vl = Vo then:
ρl × Vo < ρo × Vo
 ρl < ρo
- From this analysis, we conclude that: (Fill in the blank with the correct phrase)
- An object floats on the surface of a liquid when its density is ………………….. (greater than/equal
to/less than) the density of the liquid.
- An object floats within the liquid when its density is ………………….. (greater than/equal to/less
than) the density of the liquid.
- An object sinks in a liquid to the bottom when its density is ………………….. (greater than/equal
to/less than) the density of the liquid.