how to understand physics?!?!?

Question

question a:
How high will a 0.350 kg rock go if thrown straight up by someone who does 118 J of work on it? Neglect air resistance.
______m


question b:
A 305 kg piano slides 4.2 m down a 30° incline and is kept from accelerating by a man who is pushing back on it parallel to the incline. The effective coefficient of kinetic friction is 0.40.
1)Calculate the force exerted by the man.
______N
2)Calculate the work done by the man on the piano.
______J
3)Calculate the work done by the friction force.
______J
4)What is the work done by the force of gravity?
______ J
5)What is the net work done on the piano?
______J


question c:
A spring has k = 88 N/m. Use a graph to determine the work needed to stretch it from x = 3.8 cm to x = 4.8 cm, where x is the displacement from its unstretched length.
______J

Answer 1

Draw diagrams and put a fresh battery in your calculator.

Answer 2

I won't tell you the answers, that is for you to calculate but I will tell you how.

For the first problem set the gravitational potential energy of a mass at a given height (mgh) to the work done on the rock and solve for h. Think about why this works.

For the second problem if there is no acceleration the net force on the piano must be zero so the force of friction and the man must equal the force of gravity use this to find your unknowns.

For the third problem the relevant formula is F=kx.
Where F is the force, k is the spring constant and x the displacement.

Answer 3

Don't be spoiled and lazy!

Physics is very interesting subject. Some problems can be solved without difficult calculation. Many physics problem can be solved with only logical thinking and imagination. Like this subject, you have to draw and imagine all the forces involved and calculated with simple Newton formula.

Try to read more books and try more practices.

Answer 4

i think youc an just use conservation of energy for the first one
the U at top would be the energy put into the ball 118=mgy
so 34.4 m
i dont want to find my book to do frictions or spring

Answer 5

You'll never learn anything by relying on other people to do your work for you. You'll just fail the test that way - you won't pass the course.

Answer 6

How to understand Physics.


By studying & noodling out the answers.

Answer 7

you have the brain I bet.but it also seems that you are a bit lazy.
you can get more pleasure in solving problems(specially hard ones) by yourself than making others to solve them for you.
GOOD LUCK

Answer 8

You are not asking for help understanding physics, but asking others to do your homework - that will be no help to you at all.

Answer 9

homework sucks but it is yours to indure