We say that when a stationary train suddenly starts we tend to get a jerk back wards. As they say, it's due to inertia of rest (as the body needs to be brought in motion from rest)
Now my question is,
I don't get the fact that, how can we say that when the train is in motion, The body too is in motion. I mean, even after a jerk we continue to be in one place until we move by ourselves. I don't see any difference before and after the jerk as the body is still at rest. After all, the jerk was aiming to bring our body in motion.
Even, people say that when a stationary bus suddenly moves the sudden start of the bus brings motion to the bus as well as to our feet in contact with the floor of the bus.I don't understand this how can our feet be in motion??
Grade 9 Physics
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ctactawong
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Re: Grade 9 Physics
Hi, you can read up on Newton's first law and try to apply it to what you described.
Some questions to think about:
- The moment when the train started to move, were you at rest or moving? What would your body remain to do, according to the law?
- What pushes your body to move with the train?
- Once the train moves at a constant speed, what would your body remain to do? Do you expect to feel any force?
Some questions to think about:
- The moment when the train started to move, were you at rest or moving? What would your body remain to do, according to the law?
- What pushes your body to move with the train?
- Once the train moves at a constant speed, what would your body remain to do? Do you expect to feel any force?
Re: Grade 9 Physics
Great question! Let's break it down step by step.
1. Inertia of Rest: When the train is stationary, your body is also at rest, and it tends to stay at rest due to its property called "inertia of rest." Inertia is the tendency of an object to resist any change in its state of motion.
2. Jerk Backwards: When the train suddenly starts moving, it applies a force on your body to bring it into motion. But because of the inertia of rest, your body resists this change in motion. As a result, you feel a jerk backwards. This is because your body wants to remain at rest, but the train is moving forward, so there's a momentary conflict between your body's initial state (at rest) and the train's new state (in motion).
3. Observation Point: Here's the key point of observation. You are sitting inside the train, and your reference frame is attached to the train. When the train starts moving, you feel the jerk because your body resists the change in motion with respect to the train's frame of reference.
Now, let's address the second part of your question regarding a stationary bus suddenly moving:
1. Inertia in the Bus: When the bus is stationary, your body, including your feet, is at rest. Just like with the train, your body has inertia of rest and wants to remain at rest when the bus starts moving.
2. Feet in Motion: Here's the tricky part. When the bus starts moving suddenly, the floor of the bus exerts a force on your feet. Since your feet are in contact with the bus floor, they experience this force. As a result, the bus's motion is transferred to your feet. Your feet move along with the bus because of the force from the bus floor, even though you might not feel it immediately.
3. Observation Point: In this case, your observation point is within the bus. From this reference frame, you feel the motion of the bus, and since your feet are in contact with the bus floor, they also share that motion.
To sum it up, the key concept here is that the feeling of jerk or motion depends on your point of observation (whether you are inside the moving object or outside it) and the forces acting on your body. In both cases, the force applied to your body tries to change its initial state of rest, causing the sensation of jerk or movement. Understanding these concepts helps us grasp why we experience these effects during sudden starts of a stationary train or bus.
1. Inertia of Rest: When the train is stationary, your body is also at rest, and it tends to stay at rest due to its property called "inertia of rest." Inertia is the tendency of an object to resist any change in its state of motion.
2. Jerk Backwards: When the train suddenly starts moving, it applies a force on your body to bring it into motion. But because of the inertia of rest, your body resists this change in motion. As a result, you feel a jerk backwards. This is because your body wants to remain at rest, but the train is moving forward, so there's a momentary conflict between your body's initial state (at rest) and the train's new state (in motion).
3. Observation Point: Here's the key point of observation. You are sitting inside the train, and your reference frame is attached to the train. When the train starts moving, you feel the jerk because your body resists the change in motion with respect to the train's frame of reference.
Now, let's address the second part of your question regarding a stationary bus suddenly moving:
1. Inertia in the Bus: When the bus is stationary, your body, including your feet, is at rest. Just like with the train, your body has inertia of rest and wants to remain at rest when the bus starts moving.
2. Feet in Motion: Here's the tricky part. When the bus starts moving suddenly, the floor of the bus exerts a force on your feet. Since your feet are in contact with the bus floor, they experience this force. As a result, the bus's motion is transferred to your feet. Your feet move along with the bus because of the force from the bus floor, even though you might not feel it immediately.
3. Observation Point: In this case, your observation point is within the bus. From this reference frame, you feel the motion of the bus, and since your feet are in contact with the bus floor, they also share that motion.
To sum it up, the key concept here is that the feeling of jerk or motion depends on your point of observation (whether you are inside the moving object or outside it) and the forces acting on your body. In both cases, the force applied to your body tries to change its initial state of rest, causing the sensation of jerk or movement. Understanding these concepts helps us grasp why we experience these effects during sudden starts of a stationary train or bus.