Upthrust
An upthrust force is a force that works in an upward direction. Here students learn about the upthrust force definition, the upthrust force formula, and the upthrust force example. Also, the content connects with the mathematical concept of subtraction of numbers, comparing and ordering numbers.
What Is Upthrust Force?
When a body is immersed in a liquid, the liquid exerts an upward force. This upward force is known as Upthrust. In a liquid, a body experiences two forces:
 An upward force U (Upthrust)
 A downward force W
Upthrust Force Formula:
Upthrust Force Formula:

Upthrust Force Formula: If the bodyâ€™s weight(W) is more than the Upthrust (U) (If W > U) then the body sinks.
 If the weight of the body (W) is less than the Upthrust (U) (If W < U) then the body floats.
The formula to calculate the bodyâ€™s weight in the liquid is:
Bodyâ€™s weight in liquid = Bodyâ€™s weight in the air â€“ Upthrust
Upthrust Force Examples:
A heavy object may also float in water depends how many units of liquid it can displace.
If a steel ship and a steel ball of equal weight are placed in the water, the boat ship might float while the ball of similar weight might sink.
The reasons are:
 The ship has a flat; therefore, when it is placed in water, it displaces more liquid. Thus, the upthrust will be more than the downward sound, so it floats.
 The shape of the ball is very c. Therefore, water displaces very little liquid when it is placed in. Thus, the upthrust will be less than the downward sound, so it sinks.
Subtraction of Numbers:
Question 1:
A Wooden Block Weight 12 GF Was Placed in Water. An Upward Force Acting on the Wooden Block Due to the Water Is 4 GF. Find the Weight of the Wooden Block in the Water.
Answer 1:
Weight of the wooden block in the air = 12 gf
Upthrust due to water = 4 gf.
The formula to calculate the bodyâ€™s weight in liquid is
W_{L} = W_{A} â€“ U, where
W_{L} = Bodyâ€™s weight in liquid
W_{A} = Bodyâ€™s weight in the air
U = Upthrust due to liquid.
Substitute 12 for W_{A} and 4 for U in the formula W_{L} = W_{A} â€“ U and then simplify to get the weight of the wooden block in the water.
W_{L} = 12 â€“ 4
= 8
Therefore, the weight of the wooden block in the water is 8 gf.
Question 2:
The objectâ€™s weight in the Water and the Air Is 18 Kgf and 8 Kgf, respectively. Find the Upthrust That Will Act on the Object When Placed in Water.
Answer:
We know that W_{L} = W_{A} â€“ U. From this formula, it follows that
U = W_{A} â€“ W_{L}
Substitute 18 for W_{A} and 8 for W_{L} in the formula U = W_{A} â€“ W_{L}
and then subtract to get the upthrust.
U = 18 â€“ 8
= 10 Kgf
Thus, the upthrust due to the water is 10 Kgf.
Question 3:
Neeta Puts Two Balls, A, and B, of Weight 15 Each in the Different Swimming Pools. The Upthrust on Ball A Was 12 gf, and the Upthrust on Ball B Was 18 gf. Which Ball Will Float, and Which Will Sink? Explain.
Answer 3:
The weight of the ball A = 15 gf
Upthrust on the ball A = 12 gf
Here, 12 < 15
Since the upthrust on ball A is less than the weight of ball A (U < W).
Therefore, ball A will sink.
The weight of the ball B = 15 gf
Upthrust on the ball B = 18 gf
Here, 18 > 15
Since the upthrust on the ball B is more than the weight of the ball B (U > W). Therefore, ball B will float.