What Happens When an 80 kg Man Stands in a Lift?
The Physics Behind a Man Standing in a Lift
When an 80 kg man stands still inside a lift, it might seem like nothing special is going on. But physics-wise? Oh, there’s more happening than you think.
Let’s break it down: weight = mass × gravity. So the man’s weight, assuming Earth’s gravity (9.8 m/s²), is:
80 kg × 9.8 m/s² = 784 Newtons
That’s the force the man exerts downward on the lift floor. Simple? Sure. But it gets spicy when the lift moves.
What if the lift is at rest or moving at constant speed?
Well, in both cases, there’s no change in acceleration. The man just exerts his normal weight – 784 N. The lift floor pushes back with the same force (thanks Newton, you genius).
But if the lift accelerates or decelerates? Buckle up.
Changes When the Lift Accelerates
Going Up? Heavier.
When the lift accelerates upwards, there's a net increase in the normal force the floor pushes up with. It feels like you're being pulled into the floor – and that’s not just imagination.
If the lift accelerates at 2 m/s² upward:
Apparent weight = mass × (g + a) = 80 × (9.8 + 2) = 944 N
Whoa, feels like he gained weight, right?
Going Down? Lighter.
Now if it goes downwards, it's the opposite. The apparent weight drops:
Apparent weight = 80 × (9.8 - 2) = 624 N
Feels lighter. Like you’re floating slightly. (Kinda like that belly flip on a rollercoaster.)
What if the Lift Cable Snaps? Uh-oh.
This is the part everyone secretly thinks about – free fall.
If the lift cable breaks (yikes), and the whole thing falls freely, it accelerates down at 9.8 m/s² — same as gravity. The man would essentially be weightless.
Apparent weight = 80 × (9.8 - 9.8) = 0 N
Zero. Nada. The man and the lift fall together. That’s called free fall, and it's the same thing astronauts experience in orbit (minus the whole lift thing, of course).
Funny enough, he’d float for a moment. Terrifying? Absolutely.
The Real-World Context: Elevators and Safety
Modern lifts aren’t just random boxes dangling on cables. They have counterweights, speed sensors, emergency brakes, and tons of safety mechanisms. Free fall? Extremely rare. Like, once-in-a-blue-moon rare.
And the systems are smart enough to smooth out acceleration, so even when it speeds up or down, you usually barely feel the shift in weight (unless it’s one of those old, sketchy lifts in a 70s building... you know the ones).
Final Thoughts: It's Just Standing… or Is It?
So yeah, on the surface, an 80 kg man standing in a lift looks boring. Just a guy in a box. But underneath? It’s physics in action — forces, acceleration, inertia, the whole nine yards.
Whether he's feeling heavier, lighter, or like he's floating mid-air, it's all about the interaction between gravity and motion. Next time you're in a lift, think about it. Or don’t. But it’s kind of cool, right?
Honestly, I started this thinking “meh, not much to say about a guy in a lift”. Turns out? There's a whole world under his feet. Literally.
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Is 172 cm good for a man?
Yes it is. Average height of male in India is 166.3 cm (i.e. 5 ft 5.5 inches) while for female it is 152.6 cm (i.e. 5 ft) approximately. So, as far as your question is concerned, aforesaid height is above average in both cases.
Is 165 cm normal for a 15 year old?
The predicted height for a female, based on your parents heights, is 155 to 165cm. Most 15 year old girls are nearly done growing. I was too. It's a very normal height for a girl.
Is 160 cm too tall for a 12 year old?
How Tall Should a 12 Year Old Be? We can only speak to national average heights here in North America, whereby, a 12 year old girl would be between 137 cm to 162 cm tall (4-1/2 to 5-1/3 feet). A 12 year old boy should be between 137 cm to 160 cm tall (4-1/2 to 5-1/4 feet).
How tall is a average 15 year old?
Average Height to Weight for Teenage Boys - 13 to 20 Years
| Male Teens: 13 - 20 Years) | ||
|---|---|---|
| 14 Years | 112.0 lb. (50.8 kg) | 64.5" (163.8 cm) |
| 15 Years | 123.5 lb. (56.02 kg) | 67.0" (170.1 cm) |
| 16 Years | 134.0 lb. (60.78 kg) | 68.3" (173.4 cm) |
| 17 Years | 142.0 lb. (64.41 kg) | 69.0" (175.2 cm) |
How to get taller at 18?
Staying physically active is even more essential from childhood to grow and improve overall health. But taking it up even in adulthood can help you add a few inches to your height. Strength-building exercises, yoga, jumping rope, and biking all can help to increase your flexibility and grow a few inches taller.
Is 5.7 a good height for a 15 year old boy?
Generally speaking, the average height for 15 year olds girls is 62.9 inches (or 159.7 cm). On the other hand, teen boys at the age of 15 have a much higher average height, which is 67.0 inches (or 170.1 cm).
Can you grow between 16 and 18?
Most girls stop growing taller by age 14 or 15. However, after their early teenage growth spurt, boys continue gaining height at a gradual pace until around 18. Note that some kids will stop growing earlier and others may keep growing a year or two more.
Can you grow 1 cm after 17?
Even with a healthy diet, most people's height won't increase after age 18 to 20. The graph below shows the rate of growth from birth to age 20. As you can see, the growth lines fall to zero between ages 18 and 20 ( 7 , 8 ). The reason why your height stops increasing is your bones, specifically your growth plates.