Step 1: Calculate the speed after falling 20 m
The person starts from rest, so the initial speed is 0 . We use the formula:
v2‌=u2+2ghv‌=√2×10×20v‌=√400=20m∕sThis means after falling 20 meters, the person is moving at
20m∕s.
Step 2: Find the time to fall the first 20 m
Use the formula for distance with constant acceleration from rest:
s‌=ut+‌gt220‌=0+‌⋅10⋅t220‌=5t2t2‌=4t‌=2‌ seconds ‌So, it takes 2 seconds to fall the first 20 meters.
Step 3: Calculate the distance left after 20 m
The total height is 2000 meters. After falling 20 meters, the remaining distance is:
Remaining distance
2000−20=1980mStep 4: Find the time to travel the remaining 1980 m at constant speed
Now, the person moves at
20m∕s (from step 1). Time taken is:
t=‌=99‌ seconds ‌Step 5: Add both times to get the total time to reach the ground
Total time
=2+99=101 seconds.
