How can Newton's Laws be applied to the motion of a bus and a person on it?

In summary, the bus accelerating and causing you to fly back can be explained by Newton's 1st law, and the rocket taking off and exerting an opposite force can be described by Newton's 3rd law.
  • #1
ThomasMagnus
138
0
Hi there, I have two simple physics questions.

One day I was on the bus, and began to wonder why I kept getting thrown to the back every time the bus accelerated. Which one of Newton's laws can be applied to this?-if any.

Another question is: When a rocket takes off, it applies a force in the opposite direction. Can this be described as Newton's 3rd law: F₁=-F₁

Thanks for the help!
 
Physics news on Phys.org
  • #2
ThomasMagnus said:
One day I was on the bus, and began to wonder why I kept getting thrown to the back every time the bus accelerated. Which one of Newton's laws can be applied to this?-if any.
Newton's 1st law might shed some light. You tend to keep moving at the same speed in a straight line unless a force acts on you. When the bus accelerates, you tend to stay put until something pulls or pushes you along with the bus.

Another question is: When a rocket takes off, it applies a force in the opposite direction. Can this be described as Newton's 3rd law: F₁=-F₁
Yes, Newton's 3rd law applies. The rocket exerts a force on the exhaust gases it expels, which in turn exert an equal force on the rocket.
 
  • #3
Could Newton's third law be applied to the bus? The bus exerts a force forward and I fly back?
 
  • #4
ThomasMagnus said:
Hi there, I have two simple physics questions.

One day I was on the bus, and began to wonder why I kept getting thrown to the back every time the bus accelerated. Which one of Newton's laws can be applied to this?-if any.

Another question is: When a rocket takes off, it applies a force in the opposite direction. Can this be described as Newton's 3rd law: F₁=-F₁

Thanks for the help!

1.Newtons first law 2.yes
 
  • #5
ThomasMagnus said:
Could Newton's third law be applied to the bus? The bus exerts a force forward and I fly back?

Not until you hit the back of the seat. When the bus accelerates, it doesn't apply a force to you. You simply crash into it. However, when you do hit the seat, you will apply a force against the bus and the bus will exert a force on you, but not before that.

Suppose you and the bus are at rest at 0 m/s and you are sitting forward in your seat. When the bus accelerates, it begins to have a positive velocity while you still have 0 velocity since the force of the tires and engine are acting on the bus but not you. Soon after, the bus seat will hit you. At that point, the bus acts with a force on you that makes you accelerate until your velocity matches the bus velocity. Due to Newton's 3rd law, you also exert a force on the seat in the other direction decreasing the acceleration of the bus. However, since the bus is powered by a giant engine and you are very small compared to the bus, the force acting on the bus due to you hitting it is not noticable to the bus.
 
Last edited:

1. How are Newton's Laws applied in everyday life?

Newton's Laws can be seen in many aspects of daily life. For example, the first law explains why objects remain at rest or in motion unless acted upon by an external force. The second law is applied when calculating the acceleration of objects, such as in driving a car or throwing a ball. The third law is seen in actions and reactions, such as when a person walks or when a rocket is launched.

2. Can you give an example of an application of Newton's Second Law?

One common application of Newton's Second Law is calculating the force needed to accelerate an object. For example, when pushing a shopping cart, the force applied determines the acceleration of the cart. This can also be seen in sports, where a greater force is needed to accelerate a heavier object, such as a shot put or a basketball.

3. How is Newton's Third Law applied in engineering?

In engineering, Newton's Third Law is used to design structures and machines that can withstand forces and reactions. For example, when building a bridge, engineers have to consider the equal and opposite forces acting on the bridge to ensure it can support the weight of vehicles and withstand wind and other external forces. This law is also applied in the design of airplanes, cars, and other forms of transportation.

4. What are some real-world examples of Newton's Laws of Motion?

Some common real-world examples of Newton's Laws include the motion of falling objects due to gravity (first law), the acceleration of a car when the gas pedal is pressed (second law), and the recoil of a gun when it is fired (third law). Other examples can be found in activities such as sports, driving a car, and riding a bike.

5. How are Newton's Laws used in space exploration?

Newton's Laws play a crucial role in space exploration. The first law explains how objects in space continue to move unless acted upon by an external force, which allows spacecraft to remain in orbit. The second law is applied in calculating the acceleration and trajectory of spacecraft, while the third law is seen in the propulsion of rockets and the movement of astronauts in space.

Similar threads

Insights How to Apply Newton’s Second Law to Variable Mass Systems
    • Mechanics
Replies
0
Views
1K
I Extending Newton's laws -- Is the concept of force still defined?
    • Mechanics
2
Replies
35
Views
3K
B Newton's 3rd Law interactions with 2nd and 1st Law Partners
    • Mechanics
Replies
8
Views
324
Can Newton's Laws Be Applied in a Rotating Cabin?
    • Mechanics
Replies
2
Views
755
I Acceleration in Newton's second law
    • Mechanics
Replies
4
Views
639
Is Newton's third law valid for rotation / Torque?
    • Mechanics
Replies
23
Views
3K
Empirical and Definitional Content of Newton's Laws
    • Mechanics
4
Replies
117
Views
6K
Newton's law of cooling - formula for constant k
    • Mechanics
Replies
4
Views
2K
I Spring balance analysis from a system point of view
    • Classical Physics
Replies
24
Views
721
Why were Newton's laws of motion discovered so late?
    • Mechanics
2
Replies
66
Views
8K

Hot Threads

Recent Insights

Back
Top