Force Summation in Volleyball – Answer Key

Year 11 Physics | Teacher Use Only

Teacher:

Date:

🔵 Part 1: Multiple Choice & True/False

1. What does the principle of force summation state?

Force is generated only by the arm during a volleyball spike.

✅ Maximum force is produced by summing forces from the largest to smallest body segments in sequence.

All body segments must move simultaneously to generate maximum force.

Force is transferred from the smallest to the largest body segment.

2. In a volleyball spike, which sequence correctly applies force summation?

Wrist → Elbow → Shoulder → Trunk → Legs

✅ Legs → Hips → Trunk → Shoulder → Elbow → Wrist

Shoulder → Trunk → Hips → Legs → Wrist

Trunk → Legs → Shoulder → Wrist → Elbow

3. True or False: Each body segment adds its velocity to the next, increasing the total force applied to the ball.

✅ True

False

4. True or False: A player who only uses their arm to spike the ball will generate more force than one who uses full body sequencing.

True

✅ False

5. Which of the following best describes the role of the legs in force summation during a volleyball spike? (Select all that apply)

✅ They generate the initial and largest force in the kinetic chain.

✅ They transfer energy upward through the body.

They are the final segment to contribute force.

They reduce the force applied to the ball.

✏️ Part 2: Short Answer & Fill in the Blank

6. Fill in the blanks: Force summation requires that body segments are activated in order from largest / proximal to smallest / distal, with each segment adding its velocity / momentum to the next.

Accept reasonable variations. Key terms: largest → smallest, proximal → distal, velocity or momentum.

7. Explain why a volleyball player bends their knees before jumping to spike the ball.

Model Answer: Bending the knees loads the large leg muscles (quadriceps, glutes) and stores elastic potential energy. When the player extends, this energy is released and transferred up through the kinetic chain, contributing the largest initial force to the summation sequence.

8. A player applies a net force of 85 N to a volleyball with a mass of 0.27 kg. Calculate the acceleration of the ball. (Use F = ma)

Answer: a = F ÷ m = 85 ÷ 0.27 = 314.8 m/s² (accept 315 m/s²)

9. A player strikes the ball, which has a mass of 0.27 kg, and it leaves their hand at 18 m/s. If contact time is 0.015 s, calculate the average force applied.

Answer: Impulse = change in momentum = m × Δv = 0.27 × 18 = 4.86 N·s
Force = Impulse ÷ time = 4.86 ÷ 0.015 = 324 N

10. Describe one coaching cue a teacher could give to help a student improve force summation in their volleyball serve.

Model Answer: Examples include: "Drive up from your legs first, then rotate your hips, then swing your arm" or "Think legs → hips → shoulder → snap your wrist last." Award marks for any cue that emphasises sequential activation from large to small segments.