Fitts’ Law :Input and Interaction (Interaction Design Specialization) Answers 2026

Where:

• $a=0.8$ seconds

• $b=0.204$ s/bit (mouse) unless stated

• $d=$ distance

• $w=$ target width

✅ Question 1

• $d=935$ px

• $w=12$ px

log⁡2(935/12)=log⁡2(77.92)≈6.28\log_2(935/12) = \log_2(77.92) \approx 6.28log2​(935/12)=log2​(77.92)≈6.28 $$t=0.8+0.204\times 6.28$$ $$t=0.8+1.28=2.08$$

Answer:

2.08

✅ Question 2

• $d=67$ px

• $w=22$ px

log⁡2(67/22)=log⁡2(3.05)≈1.61\log_2(67/22) = \log_2(3.05) \approx 1.61log2​(67/22)=log2​(3.05)≈1.61 $$t=0.8+0.204\times 1.61$$ $$t=0.8+0.33=1.13$$

Answer:

1.13

✅ Question 3

• $d=105$ px

• $w=20$ px

log⁡2(105/20)=log⁡2(5.25)≈2.39\log_2(105/20) = \log_2(5.25) \approx 2.39log2​(105/20)=log2​(5.25)≈2.39 $$t=0.8+0.204\times 2.39$$ $$t=0.8+0.49=1.29$$

Answer:

1.29

✅ Question 4 (Touchpad)

• $b=0.345$ s/bit

• Start: (823, 41)

• Target: (675, 312)

• $w=30$ px

Distance:

d=(823−675)2+(41−312)2d = \sqrt{(823-675)^2 + (41-312)^2}d=(823−675)2+(41−312)2​ d=1482+2712=95345≈308.87d = \sqrt{148^2 + 271^2} = \sqrt{95345} \approx 308.87d=1482+2712​=95345​≈308.87

Apply Fitts’ Law:

log⁡2(308.87/30)=log⁡2(10.30)≈3.36\log_2(308.87/30) = \log_2(10.30) \approx 3.36log2​(308.87/30)=log2​(10.30)≈3.36 $$t=0.8+0.345\times 3.36$$ $$t=0.8+1.16=1.96$$

Answer:

1.96

🧾 FINAL ANSWERS (COPY-PASTE READY)