Can u guys help me with these 6 problems?

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In summary, the conversation was about someone asking for help with science questions related to equations of motion, Newton's second law, and kinetic energy. The person was given six questions for homework and asked for assistance and clear workings out. The conversation ended with someone providing a summary of the equations and offering further help if needed.
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hey guys, i was wondering who is good at science? The reason i am asking is because i got some 6 six questions from college, and i have some clue on how to do them? So here they are:

1. Use the equation of motion to calculate the speed and distance traveled by an object falling from rest under gravity after 3,6 and 9 seconds. Take g=10 meters per seconds squared.

2. A force of 20 N acts for 8 seconds on a mass of 60Kg. What is the (a) acceleration, (b) final speed, (c) average speed, (d) distance covered during the 8 seconds.

3. A force of 20 N is exerted on the handle of a door 0.6 meters from the hinge. If the force acts a right angles to the door, what is the moment it exerts?

4. Calculate the kinetic energy of a car of mass 1200Kg traveling at 25 m/s. If it brakes to rest at 40 meters, calculate the braking force.

5. How much heat is released by the combustion of 4Kg of petrol of calorific value 46 MJ/kg?

6. A sonar beam is radiated from a ship and an echo is received after 0.9 seconds. If the speed of sound in the water is 1400 m/s, how far away is the reflecting surface?

These are the questions i have been given for homework. So guys, please be gentle and if u can, can u also show all clear workings out. Thanks
 
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  • #2
well, what have you covered in class? For example, you will have covered Newton's second law. Do you know what it is? What relationships do you have concerning the kinetic energy of an object? Take a look at your textbook!

A little bit of reading should give you all that you need to know to do those questions. Most people here won't just do them for you. If you need help, we will be more than happy to offer it - but we do mean "help," not complete solutions.
 
  • #3
the thing is i have done science a long time ago, and i have been given these 6 six questions, which would help me get skills recognition for science. I don't exactly remember everything, hence asking for your help guys :(
 
  • #5
anyone else want to help please :)
 
  • #6
Use the equation of motion to calculate the speed and distance traveled by an object falling from rest under gravity after 3,6 and 9 seconds. Take g=10 meters per seconds squared.

Use
[tex] x = v_0t + \frac{1}{2} gt^2 [/tex] Initial velocity is zero.


The rest are similar or follow fromthis, and Newtons second law. Looking up the equations will take no more than one minute.
 
  • #7
1. Use the equation of motion to calculate the speed and distance traveled by an object falling from rest under gravity after 3,6 and 9 seconds. Take g=10 meters per seconds squared.
v(t)=gt;(1)
s(t)=(1/2)gt^2;(2)
g=10m/s^2;
so v(3)=30m/s,v(6)=60m/s,v(9)=90m/s;
and s(3)=45m,s(6)=180m,s(9)=405m.


2. A force of 20 N acts for 8 seconds on a mass of 60Kg. What is the (a) acceleration, (b) final speed, (c) average speed, (d) distance covered during the 8 seconds.
a=F/m=20/60=1/3 m/s;
v(final)=at=8/3 m/s;
V(average)=(1/2)v(final)=4/3 m/s;
S=v(average)*t=32/3 m;

3. A force of 20 N is exerted on the handle of a door 0.6 meters from the hinge. If the force acts a right angles to the door, what is the moment it exerts?
M=F*L*cosa=20*0.6=12 N*m

4. Calculate the kinetic energy of a car of mass 1200Kg traveling at 25 m/s. If it brakes to rest at 40 meters, calculate the braking force.
fs=(delta)E=(1/2)mv^2;
so f=1200*25^2/2/40=?(you caculate it yourself)

5. How much heat is released by the combustion of 4Kg of petrol of calorific value 46 MJ/kg?
E(max)=M*r=4*46=184 MJ;
E(heat)=E(max)*R (R is a ratio concerning this problem,you will find it in an engineering reference book,I don't know how to speak it in english) :smile:

6. A sonar beam is radiated from a ship and an echo is received after 0.9 seconds. If the speed of sound in the water is 1400 m/s, how far away is the reflecting surface?
2S=Vt=1400*0.9=1260 m;
so S=630 m.

If you still have any question about these problem,please contact me at wangkehandsome@hotmail.com.I will be glad to anwser it for you.
 

1. What kind of problems are you seeking help with?

I have six problems related to my research or experiment that I need assistance with.

2. Can you provide more details about the problems?

Yes, I can provide specific information and background about each problem and what I have tried so far.

3. Are these problems related to a specific scientific field?

Yes, these problems are related to a specific scientific field, such as biology, chemistry, physics, etc.

4. How urgent is your need for help with these problems?

The urgency of my need for help with these problems varies. Some may be time-sensitive, while others can be addressed at a later time.

5. Can you explain why you need help with these problems?

I am seeking help with these problems because I have exhausted my own knowledge and resources, and I believe that seeking assistance from other scientists can help me find a solution or approach the problems from a different perspective.

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