1Calculation
Warm-Up Challenge: A person with a mass of 68 kg stands still on the floor. What is their approximate weight force on Earth? Use g = 9.8 m/s².
2Short Answer
A runner pushes backward on the ground with a force of 450 N. According to Newton’s third law, what force does the ground exert on the runner, and in what direction?
3Calculation
A doctor estimates the pressure in a fluid inside the body using P = F/A. If a force of 24 N acts on an area of 0.003 m², what is the pressure?
4Calculation
A person takes one step and their center of mass rises by 4 cm. If their mass is 70 kg, about how much gravitational potential energy is gained? Use g = 9.8 m/s².
5Calculation
Heart Challenge: The heart pumps 70 mL of blood with each beat. If it beats 72 times per minute, how much blood is pumped in 1 minute?
6Calculation
A person lifts a 12 kg box from the floor to a shelf 1.5 m high in 3 seconds. What is the average power output of the lift? Use g = 9.8 m/s².
7Short Answer
Why do feet often feel more pressure in high-heeled shoes than in flat shoes, even if body weight stays the same?
8Short Answer
Challenge Problem: A blood vessel narrows to half its original radius. If blood flow rate must stay the same, what happens to blood speed in that narrowed section?
9Short Answer
The biceps muscle pulls on the forearm with a force of 300 N while the hand holds a 40 N weight. If the hand is 0.30 m from the elbow and the biceps attaches 0.05 m from the elbow, which force creates the larger turning effect, and why?
10Extended Response
Final Boss: A person’s breathing rate increases during exercise because their body needs more oxygen and produces more carbon dioxide. Explain this using at least two physics ideas from this worksheet, such as energy, flow, pressure, or work.
Answer Key
Teacher Notes:
Use this worksheet for adult learners reviewing mechanics, pressure, energy, and fluid flow in the human body. Suggested classroom use: warm-up, guided independent practice, or small-group challenge station. Learning objectives: apply physics concepts to body systems, analyze real-life body movement and circulation, and solve quantitative problems with units. Extension ideas: have students compare blood pressure to fluid pressure in other systems, or model joint forces during lifting. Differentiation: support struggling learners with a formula bank and unit hints; challenge advanced learners to justify assumptions and estimate uncertainties.
| # | Answer | Explanation |
|---|
| 1 | About 666 N | Weight force equals mass × gravity: 68 × 9.8 = 666.4 N, which rounds to about 666 N. |
| 2 | The ground exerts an equal force of 450 N forward on the runner. | Newton’s third law says forces come in equal and opposite pairs. If the runner pushes backward, the ground pushes forward with the same magnitude. |
| 3 | 8,000 Pa | Pressure = force ÷ area = 24 ÷ 0.003 = 8,000 pascals. |
| 4 | About 27.4 J | Use U = mgh. Convert 4 cm to 0.04 m: 70 × 9.8 × 0.04 = 27.44 J, about 27.4 J. |
| 5 | 5,040 mL per minute, or 5.04 L per minute | Multiply stroke volume by heart rate: 70 × 72 = 5,040 mL, which is 5.04 liters. |
| 6 | About 58.8 W | First find work: W = mgh = 12 × 9.8 × 1.5 = 176.4 J. Then power = work ÷ time = 176.4 ÷ 3 = 58.8 W. |
| 7 | Because the same weight is supported by a smaller contact area, so pressure increases. | Pressure equals force divided by area. If force stays the same and area gets smaller, pressure becomes larger. |
| 8 | Blood speed increases by a factor of 4. | Cross-sectional area is proportional to radius squared. Halving the radius reduces area to one-fourth, so speed must increase fourfold to keep flow rate constant. |
| 9 | The 40 N weight creates a larger turning effect because it acts farther from the elbow. | Torque depends on force × distance from the pivot. The biceps force is larger, but it acts much closer to the elbow. 300 × 0.05 = 15 N·m, while 40 × 0.30 = 12 N·m, so the biceps still creates the slightly larger torque here. |
| 10 | Sample answer: During exercise, muscles use more energy, so the body needs more oxygen for respiration and must remove carbon dioxide faster. Breathing rate increases to move a larger volume of air in and out of the lungs per minute. This improves gas exchange by increasing airflow and supporting diffusion. The body is also doing more work, which raises energy demand and heat production, so faster breathing helps meet the higher physical needs. | A strong response links increased energy demand to faster air flow and gas exchange, using physics ideas such as work, energy, pressure differences, and flow rate. |