Photo AI
6. (a) Figure 11 shows a person doing a push-up exercise - Edexcel - GCSE Physics - Question 6 - 2023 - Paper 2
Question 6
6. (a) Figure 11 shows a person doing a push-up exercise. An upward force is used to cause rotation about a pivot. Which row of the table is correct for this rotat... show full transcript
Worked Solution & Example Answer:6. (a) Figure 11 shows a person doing a push-up exercise - Edexcel - GCSE Physics - Question 6 - 2023 - Paper 2
Step 1
An upward force is used to cause rotation about a pivot. Which row of the table is correct for this rotation?
Answer
The correct row for the upward force and pivot in a push-up exercise is: A: arms provide the upward force, hands act as a pivot. This is because during a push-up, the arms are exerting an upward force while the hands remain fixed on the ground, allowing rotation about the elbow joint.
Step 2
Use the principle of moments to show that the system shown in Figure 13 is in equilibrium.
Answer
To demonstrate equilibrium using the principle of moments, we will set the clockwise moments equal to the counterclockwise moments. In Figure 13:
-
Calculate the moment due to the weight of the forearm:
ext{Moment} = ext{force} imes ext{distance} = 23 ext{ N} imes 16 ext{ cm} = 368 ext{ Ncm}
-
Calculate the moment due to the biceps force:
ext{Moment} = 92 ext{ N} imes 4 ext{ cm} = 368 ext{ Ncm}
-
Total clockwise moments:
ext{Total Moments} = 368 ext{ Ncm} + 480 ext{ Ncm} = 848 ext{ Ncm}
Thus, since the total moments are equal, the system is in equilibrium.
Step 3
Calculate the force from the muscle that is needed to keep the system in Figure 14 in equilibrium.
Answer
To find the force from the muscle to keep the system in equilibrium:
-
Calculate the moment due to the ball:
ext{Moment} = ext{weight of ball} imes ext{distance} = 15 ext{ N} imes 32 ext{ cm} = 480 ext{ Ncm}
-
Total clockwise moment:
ext{Total Moments} = 480 ext{ Ncm} + 368 ext{ Ncm} = 848 ext{ Ncm}
-
Calculate the needed muscle force using the distance from the elbow joint:
ext{Force} = rac{ ext{Total Moments}}{ ext{distance}} = rac{848 ext{ Ncm}}{4 ext{ cm}} = 212 ext{ N}
Therefore, the required muscle force is 212 N.
Step 4
Compare the upthrust on the ball in seawater with the upthrust on the same ball in fresh water.
Answer
The upthrust exerted on the ball is greater in seawater than in fresh water because seawater is denser than fresh water. As a result, the buoyant force, which depends on the volume of fluid displaced, is higher in seawater.
Step 5
Explain why there is less of the ball below the surface of the seawater than below the surface of the fresh water.
Answer
This occurs due to the density differences between seawater and fresh water. Sea water has a higher density, resulting in a greater upthrust for the same volume of displaced water. Consequently, a ball floating in seawater displaces less volume compared to when it is in fresh water, leading to less of the ball being submerged below the surface of the seawater.