Find the correct answer and tell me.?

Question

Why do we move forward with a jerk when a bus stops?

Also explain the answer.

Answer 1

It's based on the Law of Inertia. A body at rest tends to stay at rest unless acted on by an external force. Also, a body in motion tends to stay in motion unless acted on by an external force.

When the bus is stopping, the friction of the brakes are stopping the bus. However, a person tends to continue to move forward. The friction of our clothes to the seat or a handrest, and even our internal muscles helps to "slow us down", but we still want to continue forward...

Answer 2

Perhaps you're speaking most of the jerk just as the bus comes to a *complete* stop, not just when it begins to brake. The brakes on the bus (or a car for that matter) use sliding friction, but just as you come to a stop friction jumps quickly as the speed of the brake pad over the rotor becomes very very low as static friction takes hold.

When you learn to drive a car you tend to learn to let off the brake slightly right when you get to very low speed, right before you come to a complete stop. You may not notice this as it is something new drivers learn quickly.

Buses use different braking systems, so it may be harder for the driver to smooth out the end of a stop, or it may be an inherent limit of the air brakes. However, I admit I've never driven a bus. Buses are usually on schedules, thus they may be trying to stop quickly rather than making the last moment of a stop smooth.

Either way, this is not just something that happens on buses. Go stop a car from, say, 20mph, but be sure to hold the brake with exact constant pressure as best you can and you will jerk like you describe just as the car reaches a complete halt. Or watch someone else drive, you'll notice they unconsciously let off the brake ever so slightly just as the car comes to a stop.

Answer 3

Conservation on linear momentum and conservation of kinetic energy. You aren't attached to the bus. So you are moving with the speed the bus is moving. If it suddenly breaks, the firction forces that keep you from sliding off your seat or off your feet if you are standing, are weak enough that you can ignore then to first order. So if the bus were moving with a speed v, which means you are as well, and the bus suddenly stops, you have a linear momentum mV (where m is your mass) that has to be conserved if there are no other forces acting on you.

Force is the rate of change of momentum with time or the derivative of momentum with time. Let's say the bus goes from 10 m/s to 0 in 0.5 seconds and has a mass of 2000 kg. The the force acting on the bus from its brakes is about 40,000 Nts. Now lets say you are sitting in the bus and your mass is 50 kg. You'd need a frictional force of 50kg*10m/s/0.5 sec = 2500 Nts to keep you from jerking forward. Friction might be a force of ~0.2*50kg*10 m/s^2 ~ 100 Nts. So with no other forces acting on you, you jerk forward. In this case you experience an acceleration of
a =(2500 - 100)/50 = 48 m/s^2 or almost 5 times the acceleration due to gravity.

Answer 4

We jerk forward when the bus stops because of the law of inertia.

The law states that no matter moves unless "pushed" by another matter in motion. it is a case of cause and effect.

While no one really pushes us when we are inside the bus,
we are affected by a "gravity effect" inside the bus only because of the sheer mass (weight) of the bus. Its mass
causes us to be "carried" or affected by the bus' motion.

We can illustrate our point on a smaller scale. Take a small carton box, say 1 foot by 1 foot by 1 foot. Put two marbles in it and shake the box. The marbles will move when the box is shaken, even if it stays level perfectly. That's because the mass of the box overpowers the weight of the marbles and causes them to move.

Have a great and blessed weekend. Now with this mystery solved, we can go outside and play "marbles:"

Answer 5

"a body in motion tends to stay in motion unless acted upon by an outside force"

People sitting on a bus are in motion, but they are traveling at the same speed as the bus and have the illusion of being motionless. The bus uses its brakes to come to a stop. The people on the bus are also stopping but people have no brakes. Brakes are what the bus uses to prevent it from moving foreward. People have to push back against the floor with their legs. Brakes are designed to slowly stop a movingt vehicle; if the bus were to hit a wall, the passengers would be thrown foreward at the same speed they were traveling before the bus came to an instantaneous stop.

Answer 6

Inertia, it is one of Newtons Laws of motion. It states...
"An object in motion will stay in motion, and an object at rest will stay at rest until act on by an outside force" The bus was in motion and you were in motion. The buses outside force was the brakes. Even if in your mind you know the bus is going to stop, physically you don't. Your outside force is the seat in front of you. It stops you. This works with everything. Drop a ball from someplace. That ball is going to keep falling until it gets acted on by an out side force the ground. Throw it un. Its going to keep going until it gets acted on by an outside force, gravity.
I hope I helped
Good luck

Answer 7

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Answer 8

it is because oft he property of INertia of our body. OUr body which was in motion in the moving bus tends to continue its forward motion though the bus and your seat has stopped. the seat stops your bottom because of force of friction but the upper part of your body continues it motion.

Answer 9

newtons 1st law. its the law of inertia. even though the bus has stopped moving, the bodies are still moving.

Answer 10

yeah, this is in a way how sattelites stay up in space orbiting earth..if the planet just suddenly stops, the sattelite would just keep on going for a bit longer....