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by Ron Kurtus

A total of 162 comments and questions have been sent in. They are listed according to date.

## List of next 10 letters

### Country

Characteristics of Force Problem of object on smooth table Canada

Inertial and Real Forces How is a fly affected when a bus slows down? India

Force and Motion Why is it there is gravity Philippines

Characteristics of Force Want examples about static force Somalialand

Forces How to accelerate an object? USA

Characteristics of Force Characteristics of a force UK

Characteristics of Force What are the effects of forces? Pakistan

Force Stopping a man falling off a roof USA

Force Difference between force and load India

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First 10 letters

## Problem of object on smooth table

Topic: Characteristics of Force

### Question

October 23, 2010

How to solve this problem:
Suppose the only horizantal forces acting on a 20N object on a smooth table are 36N (45 degree) and 60N (125 degree)
a- what is the net force acting on the object
b- calculate acceleration of the object

20570

It is not clear what the configuration is in this problem.

What is the mass of the 20N object--or is that a typo?
Is the 36N force horizontal on a table at 45 degrees?
Are you looking for acceleration of the object due to gravity when it slides on a tilted table?

In any problem, the factors must be clearly stated so that there are no misunderstandings.

## How is a fly affected when a bus slows down?

Topic: Inertial and Real Forces

### Question

July 11, 2010

A fly is moving inside a bus in the diraction in which the bus is moving. If brakes are applied to the bus will he motion of the fly be affected? Will it move backward like the passengers of the bus? Please explain your answer with a reason.

hiral - India

20037

All the things in the bus--the fly, the air and the people--are moving forward at the same speed as the bus, with respect to the ground outside. This can be see by someone outside the bus.

When the brakes are applied, the bus slows down, but all the things continue to move forward at the previous speed. People can prevent this motion by grabbing onto things. The fly also moves forward. But it can remain in the same position if it flies toward the back at a sufficient speed.

## Has different theories about gravity and forces

Topic: Characteristics of Force

### Question

June 13, 2010

Hi Ron Kurtus,

Your page states: Force at a distance is strange.

That's because it doesn't really exist. Gravity is a pushing force of Mass Expansion. It does not "pull" through empty space.

Best wishes, ;0)

www.EinsteinGravity.com

19886

Gravity has been defined as a force at a distance, as caused by a curvature in space and as an exchange or graviton particles. Your concept of gravity being a force of mass expansion is interesting, but I am not sure it is accepted by most scientists.

Electrical and magnetic forces also act at a distance, but I am not sure how they fit in your theory.

You need to be more distinct in your statements. For example, gravity is not 9.8 m/s^2. That number should be stated as the "acceleration due to gravity". This should help clarify your concepts.

## Why is it there is gravity

Topic: Force and Motion

### Question

February 9, 2010

why is it there is gravity if there is a mass.

Gil Dominard - Philippines

19185

Gravity or gravitation is a property of every object that has mass.

See our section on gravity: http://www.school-for-champions.com/science/gravity.htm

## Want examples about static force

Topic: Characteristics of Force

### Question

December 26, 2009

can u give some examples about static force?

abdiaziz - Somalialand

18926

See "Static Electricity Forces" at:
http://www.school-for-champions.com/science/static_forces.htm

However, if you are talking about a static force where something is not moving, see http://www.school-for-champions.com/science/friction.htm

## How to accelerate an object?

Topic: Forces

### Question

December 7, 2009

what must happen for someone to accelerate their velocity

haylee - USA

18805

Any force will accelerate an object provided any opposite forces holding it back are less the the accelerating force. If you push and slide an object on the floor, it will accelerate, provided the friction is not too great. Likewise, the force of gravity will accelerate an object, provided air resistance is not too great.

## Characteristics of a force

Topic: Characteristics of Force

### Question

September 28, 2009

what are the three characteristics of a force

nor - UK

18402

A force changes velocity and direction, depending on the mass of the object.

## What are the effects of forces?

Topic: Characteristics of Force

### Question

August 30, 2009

could you please describe the effects of forces? with their examples???

ben - Pakistan

18229

A simple explanation of a force is that it is a push or a pull. When you push on a door, you are exerting a force on the door. The wind can exert force on a boat, causing it to move. Gravity is a force that pulls you toward the ground.

## Stopping a man falling off a roof

Topic: Force

### Question

March 17, 2009

Can you tell me/show me how to calculate the force necessary to stop a falling object. e.g. a 150 pound man falls off a building after 6 feet he is stopped by a rope. What force is applied to the rope to stop the falling man?

Robert - USA

17452

Force equals mass times acceleration (or in this case, deceleration).

Look at the lesson on Gravity Equations for Falling Objects at:
http://www.school-for-champions.com/science/gravity_equations_falling.htm

You can get the speed the person reaches after falling 6 feet, which is about 20 ft/s.

The problem with the question is that information about the elasticity or stretch of the rope is missing. Acceleration or deceleration is the change in velocity over a short period of time, where the rope would slow the fall until zero velocity. That would take a fraction of a second. Otherwise, the man would bounce back up to the top for a "perfect" rope.

The force to stop the man and the force on the rope are the same and require knowledge of how long the rope takes to stop his motion. With that time, you would get F = mass*20/T or weight*20/T.

## Difference between force and load

Topic: Force

### Question

February 19, 2009

Dear sir
what is the difference between force and load

pratyusha - India

17297

Force is a push or pull on an object, caused by another object.

Load is used in engineering to mean the force exerted on a surface or body. It is the force applied to a component of a structure.

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