by Ron Kurtus
You can read them to further your understanding of the subject.
|Forces||Force to stop a truck||Ireland|
|Forces||This is a really good website||England|
|Forces||Accelerating a crate||Australia|
|Forces and Torque||How do super fast trains work without friction?||India|
|Forces and Torque||Have to assemble over 20,000 pulleys||Brisbane Australia|
|Forces||How do you convert fractions into decimals?||UK|
|Forces||5 main key words in force||UK|
|Forces||Could you tell me about air resistance?||England|
|Forces||Stopping a heavy truck versus a light truck||USA|
|Forces||Comparing punch with fist and boxing glove||USA|
Force to stop a truck
September 5, 2006
If a truck has a mass of 60tonnes and is travelling at 80k/h what is its kinetic energy and how much force would it take to stop it if its brakes failed?
If the same truck was travelling down a 5degree gradient, what force would then be needed to stop it.
Joseph - Ireland
Kinetic energy = mass x velocity squared, divided by 2. So, you have 60 x 80 x 80 / 2.
Force equals mass times acceleration. In order to know the force required to stop the truck, you need to know how fast it is supposed to stop. It takes less force to stop the truck in 1 minute than in 1 second.
This is a really good website
September 1, 2006
This is a really good website. Very helpful. I've sent a couple of questions already. I visited once when I was a week away from my sats in yr 6
Brooke - England
Thanks for the feedback. I'm glad you like the site.
Accelerating a crate
August 13, 2006
I was wondering, if you apply a constant force to something, like when pulling a crate, does it accelerate? why? How then do you pull something and get it to travel at a constant speed?
Annette - Australia
When you start from zero speed and go up to some other speed, you are accelerating the object. Acceleration is the change in speed or velocity. If there was no friction, an object would continue to travel at a constant speed. Otherwise you need to apply just enough force to equal the force of friction.
How do super fast trains work without friction?
Topic: Forces and Torque
July 29, 2006
SIr we know that friction provides the force for a vehicle to move. But tehn hiow does suoper fast trains move when we know that their wheels arnt in direct contact with the rails?
Ayush - India
In a normal vehicle, such as an automobile, the engine provides a torque on the wheels. Friction resists the torque, causing the vehicle to move forward. Remember that friction is a resistive force.
The super fast trains are often called mag-lev trains, because a magnetic force powers the motion. They go fast because no friction resists the motion.
Have to assemble over 20,000 pulleys
Topic: Forces and Torque
May 11, 2006
Good Morning, I have to assemble over 20,000 pulleys with 2 bearings and 1 shaft per pulley, they have to rotate freely about the shaft with a maximum initial torque no greater than .34 n/m or 3 lb.in., is there a device or a machine that i can use to apply and measure this load.
Mike - Brisbane Australia
Good golly! It will take you forever to assemble over 20,000 pulleys. I assume your initial torque is for the whole system and not each individual pulley. With so many pulleys, the initial force would be enormous.
The torque divided by the radius of a pulley should give you the force required to turn it. A simple spring scale should measure that force.
How do you convert fractions into decimals?
April 22, 2006
How do you convert fractions into decimals and decimals into fractions?
Pooja - UK
The "/" sign in a fraction means "divided by." Thus, a fraction such as 12/36 means "12 divided by 36". When you divide it out, you will get a decimal, such as 0.333.
Going the other direction is not as easy. A decimal such as 0.1 equals 1/10, 0.23 = 23/100, and 0.224 = 224/1000. You can simplify the fractions, like 224/1000 = 28/125.
5 main key words in force
April 20, 2006
i would really appreciate it if you helped me on this subject so that i could better at science because it is my favourite subject.
what are the 5 main key words in force, i only know two of them
and please i need the answer as soon as possible please.
stephanie - UK
I'm sorry, but I'm not sure what your teacher means by that. I guess you could say: mass, push, pull, acceleration, and pressure.
Could you tell me about air resistance?
April 4, 2006
could you tell me more about air resistance and how this force works?
Brooke - England
When moving an object through a fluid like air or water, the object must move the fluid out of the way. When moving through air, the force required to move the air out of the way is called the air resistance.
If the object is streamlined, then the air easily moves out of the way and the air resistance is small. If you place the palm of you hand out the window of a moving car, you can feel the air resistance on something that is not streamlined.
Air resistance is a force that moves in the opposite direction of motion, slowing things down. In that way, it is similar to the force of friction.
Stopping a heavy truck versus a light truck
March 23, 2006
does it require more work to stop a light truck or heavy truck moving with the same momentum? i thought it would be the heavy truck because it has more mass.
This problem requires a logical look at the situation:
Work = force times distance. Force = mass times acceleration. Acceleration = change in velocity. Momentum = mass time velocity.
If the trucks have the same momentum, the heavier truck is going slower. Thus, its acceleration (or deceleration in the case of slowing down) is less. That means the force to stop the heavy truck is less. Since they travel the same distance to the red light, the work is less to stop the heavy truck.
Comparing punch with fist and boxing glove
March 23, 2006
Why is a punch more forceful with a bare fist than with a boxing glove?
A boxing glove absorbs some of the force, spreading the energy through the material. The cushioning effect of the boxing glove means that the force of the blow is not as immediate as when hitting with a hard fist.
Hopefully, this reader feedback has helped provide information about Force issues.
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