Free fall: Class 9 practice
A freely falling body has acceleration g (take 9.8 or 10 m/s²) downwards. Read the method, follow the three worked examples, then try the six questions.
What you should know first
- Equations of motion
The idea behind free fall
A freely falling body has acceleration g (take 9.8 or 10 m/s²) downwards. Use v = u + gt, h = ut + ½gt², v² = u² + 2gh. Thrown up, it slows at g until v = 0 at the top.
Step-by-step method
- Choose up or down as positive.
- Write u, a = ±g and what is asked.
- Pick the equation that contains the knowns.
Worked example 1 (Basic)
A stone is dropped from rest. Find its speed and distance fallen after 4 s (g = 10 m/s²).
- v = gt = 40 m/s
- h = ½gt² = 80 m
- Answer: 40 m/s, 80 m
Worked example 2 (Standard)
A ball is thrown up at 20 m/s. Find the maximum height and time to reach it (g = 10 m/s²).
- H = u²/2g = 20 m
- t = u/g = 2 s
- Answer: 20 m, 2 s
Worked example 3 (Challenge)
A body falls from rest through 25 m. Find its speed on reaching the ground (g = 10 m/s²).
- v² = 2gh = 500
- v = 22.36 m/s
- Answer: 22.36 m/s
Common mistakes and misconceptions
- Using g = +10 upwards
- Forgetting v = 0 at the top
Practice questions
- (Basic) A stone is dropped from rest. Find its speed and distance fallen after 2 s (g = 10 m/s²).
- (Basic) A stone is dropped from rest. Find its speed and distance fallen after 6 s (g = 10 m/s²).
- (Standard) A ball is thrown up at 60 m/s. Find the maximum height and time to reach it (g = 10 m/s²).
- (Standard) A ball is thrown up at 30 m/s. Find the maximum height and time to reach it (g = 10 m/s²).
- (Challenge) A body falls from rest through 80 m. Find its speed on reaching the ground (g = 10 m/s²).
- (Challenge) A body falls from rest through 45 m. Find its speed on reaching the ground (g = 10 m/s²).
Answer key with full working
- Q1: v = gt = 20 m/s → h = ½gt² = 20 m → Answer: 20 m/s, 20 m
- Q2: v = gt = 60 m/s → h = ½gt² = 180 m → Answer: 60 m/s, 180 m
- Q3: H = u²/2g = 180 m → t = u/g = 6 s → Answer: 180 m, 6 s
- Q4: H = u²/2g = 45 m → t = u/g = 3 s → Answer: 45 m, 3 s
- Q5: v² = 2gh = 1600 → v = 40 m/s → Answer: 40 m/s
- Q6: v² = 2gh = 900 → v = 30 m/s → Answer: 30 m/s
Syllabus note
This skill is listed under "Gravitation" for Class 9 in the NCERT/CBSE books. ICSE, IGCSE, IB and state boards may teach it in a different chapter or year.
Answers on this page are generated and automatically re-checked by a second, independent calculation. They have not been reviewed by a teacher — if you spot a problem, tell us on WhatsApp.
Related practice and notes
Frequently asked questions
Which chapter is free fall in?
"Gravitation", Class 9 Physics (NCERT/CBSE). Other boards may place it differently.
How were the answers checked?
Answers on this page are generated and automatically re-checked by a second, independent calculation. They have not been reviewed by a teacher — if you spot a problem, tell us on WhatsApp.