Jumping on a boat that is moving

• Eric Berger
In summary, a video of a group of guys on a boat hitting a big wave and one guy jumping in the air and landing almost exactly where he started has sparked the question of why this happens. Since the guy is on the boat, he is going the same speed as it, but there is still air resistance that could potentially slow him down. However, the force of air resistance is too small to significantly affect his speed during the brief time he is airborne. When considering the up-and-down movement separately, it is no different than jumping on land and the horizontal speed of the boat has no effect. Overall, this phenomenon can be better understood through Newton's First Law of Motion, and further clarification can be gained by taking physics.
Eric Berger
Hello PF, I am a junior in high school who has yet to take physics and is currently in Honors Chem. I recently saw a video on social media, where a group of guys is on a big boat and this one guy was standing relatively close to the bow. And they hit a big wave and he jumps in the air and lands almost exactly where he started. And i have been sifting through other threads and information but can't seem to find an answer. Why does this happen, isn't there air resistance and such. But he is on the boat so he must be going the same speed as it. I am absolutely baffled and confused, so i turned to you people of great intelligence to help me.

Here is the video if you were curious (https://www.instagram.com/p/BdRWcVTj_Em/?hl=en&taken-by=barstoolsports)

Thank you
-Eric

Eric Berger said:
Why does this happen, isn't there air resistance and such. But he is on the boat so he must be going the same speed as it.

You are correct. He is going the same speed as the boat, and he keeps that speed when he is up in the air. The air resistance is pushing him back, just not enough to notice. Your observations are good, and the rest will make sense when you take physics.

lekh2003 and Eric Berger
Eric Berger said:
Hello PF, I am a junior in high school who has yet to take physics and is currently in Honors Chem. I recently saw a video on social media, where a group of guys is on a big boat and this one guy was standing relatively close to the bow. And they hit a big wave and he jumps in the air and lands almost exactly where he started. And i have been sifting through other threads and information but can't seem to find an answer. Why does this happen, isn't there air resistance and such. But he is on the boat so he must be going the same speed as it. I am absolutely baffled and confused, so i turned to you people of great intelligence to help me.

Here is the video if you were curious (https://www.instagram.com/p/BdRWcVTj_Em/?hl=en&taken-by=barstoolsports)

Thank you
-Eric
Think of the up-and-down movement as being separate to the horizontal movement.
Newton's First Law says that objects keep moving with the same velocity unless acted on by a force. So if air resistance is negligible, he will continue at boat speed when he is in the air.
Of course, air resistance will slow him down a little, but if we assume a boat speed of 5m/s, the force is too small to slow him significantly during the brief interval he is airborne.
Regarding the up-and-down movement, it is no different to making the jump ashore, and he will be in the air for the same time. The horizontal speed of the boat has no effect, although I agree the boat pushed him up at just the right moment, which would not happen ashore.

JRMichler said:
You are correct. He is going the same speed as the boat, and he keeps that speed when he is up in the air. The air resistance is pushing him back, just not enough to notice. Your observations are good, and the rest will make sense when you take physics.
Sorry Eric, I did not spot your reply.

tech99 said:
Of course, air resistance will slow him down a little, but if we assume a boat speed of 5m/s, the force is too small to slow him significantly during the brief interval he is airborne.
You can 'feel' the force of a 5m/s wind against your face so the same pressure is acting over the whole area of your body facing the wind, which would correspond to a small but significant force. Remember that sailing boats (albeit with large sails) will sail happily in an 11mph wind. A though experiment on a boat adds several extra factors that can get in the way of understanding what's going on. If you imagine hanging on a bar with a 5m/s wind blowing on you (preferably a stationary dummy.). The feet are 0.5m above the ground. In the time taken to fall (about 0.2s) that force will move you a small amount - enough to measure a movement along the ground.

Eric Berger said:
Hello PF, I am a junior in high school who has yet to take physics and is currently in Honors Chem. I recently saw a video on social media, where a group of guys is on a big boat and this one guy was standing relatively close to the bow. And they hit a big wave and he jumps in the air and lands almost exactly where he started. And i have been sifting through other threads and information but can't seem to find an answer. Why does this happen, isn't there air resistance and such. But he is on the boat so he must be going the same speed as it. I am absolutely baffled and confused, so i turned to you people of great intelligence to help me.

Here is the video if you were curious (https://www.instagram.com/p/BdRWcVTj_Em/?hl=en&taken-by=barstoolsports)

Thank you
-Eric

This is no different than jumping on the earth, which is moving with respect to other celestial bodies.

Zz.

PeroK
The wind starts to blow him back when his feet leave the boat. The distance he is blown back can be estimated, given some assumptions:
Estimated wind speed: 20 MPH
Estimated frontal area of the boy: 5 ft^2 (he's skinny)
Estimated Cd of the boy: 1.0
Estimated weight: 150 lbs
Estimated time in the air: 0.9 seconds

Velocity pressure of air at 100 MPH is 25 lbs/ft^2, so the velocity pressure at 20 MPH is (20/100)^2 X 25 = 1.0 lbs/ft^2.
Total force of wind on the boy is 1.0 lbs/ft^2 X 1.0 Cd X 5 ft^2 = 5 lbs.
Acceleration = 5 / 150 X 32.2 = 1.07 ft/sec^2.
Distance = 0.5 X 1.07 ft/sec^2 X 0.9^2 sec^2 = 0.4 feet = 5 inches.

If he jumps slightly forward on his way up, he will land exactly where he takes off.

JRMichler said:
If he jumps slightly forward on his way up, he will land exactly where he takes off.
And by no coincidence, he will already be leaning forward at the right angle to accomplish just that.

JRMichler

1. What is the risk of jumping on a boat that is moving?

Jumping on a moving boat can be dangerous as it can result in injury or falling overboard. The boat's movement can also cause you to lose your balance and potentially collide with other objects on the boat.

2. Can jumping on a moving boat damage the boat?

Yes, jumping on a moving boat can potentially damage the boat's structure or equipment. The impact of your body hitting the boat can cause dents, scratches, or even breakages. This can also lead to costly repairs.

3. Is it easier to jump on a fast-moving boat or a slow-moving boat?

It is not recommended to jump on any moving boat. However, it may be easier to jump on a slow-moving boat as there is less risk of falling overboard or losing your balance. It is always best to wait for the boat to come to a complete stop before attempting to jump on it.

4. Are there any safety precautions to take when jumping on a boat that is moving?

Yes, there are several safety precautions to take when jumping on a boat that is moving. These include wearing a life jacket, ensuring a clear and safe landing spot, and communicating with the boat's driver to ensure they are aware of your intentions.

5. Can jumping on a moving boat be considered a water sport or activity?

No, jumping on a moving boat is not a recognized water sport or activity. It is not safe or recommended to do so, and it can lead to serious injury or accidents. It is important to always follow proper safety guidelines when participating in water sports or activities.

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