Me I Am So Terrible At Physics

[malajube]

Please Help Me! I Am So Terrible At Physics!

Hi everyone! I am new here and I am asking this question because this year I enrolled in Physics, and my teacher is horrible. On a practice test, we have 3 questions that I just cannot figure out!
Could you all help me? I don't need answers, I just can't understand the formulas, or which ones to use. If you all could just tell me what formulas, I could piece together the rest!

Thank you!
Anna

1) Water flows over a section of Niagra Falls at the rate of 1.2 x 10E6 (to the sixth) kg/s and falls 50.0 m. How much power is generated by the falling water?
a) 9.50 x 10E6 W
b) 5.90 x 10E8 W
c) 1.04 x 10E5 W
d) 6.40 x 10E4 W



2) A 70.0 kg base runner begins his slide into second base while moving at a speed of 4.0 m/s. The coefficent of friction between his clothes and Earth is .70 . He slides so that his speed is 0 just as he reaches the base. How much mechanical energy is lost?
a) -8.4 x 10E2 J
b) -2.3 x 10E3 J
c) -5.6 x 10E2 J
d) -9.5 x 10E4 J


3) (Cont. from question 2) How far does he slide?
a) 1.2 m
b) 5.1 m
c) 8.3 m
d) 3.7 m

 

[learningphysics]

For the first question, deal with energy first before power... in 1s, how much energy is produced... think gravitational potential energy.

For the second question, what is the formula for kinetic energy?

For the third... what is the force of friction... through what distance does the force of friction act to bring the energy of the runner to 0.

 

[m2003]

Hi Anna,

I'm sorry to hear that you're struggling with Physics. It can be a challenging subject, but with some practice and understanding of the key concepts and formulas, you can definitely improve!

For the first question, you will need to use the formula for power, which is P = W/t (power = work/time). In this case, the work is equal to the weight of the water multiplied by the height it falls, which is given as 50.0 m. The time is not given, but you can calculate it by dividing the mass of water (1.2 x 10^6 kg) by the rate of flow (also given in kg/s). Once you have calculated the work and time, you can plug them into the formula to calculate the power generated by the falling water.

For the second question, you will need to use the formula for mechanical energy, which is E = mgh (mechanical energy = mass x gravity x height). In this case, the mass is given as 70.0 kg, the height is not given but you can assume it is equal to the distance the runner slides (which you will calculate in the next question), and the gravity can be taken as 9.8 m/s^2. You will also need to use the coefficient of friction to calculate the work done by friction, which is W = Fd (work = force x distance). The force can be calculated using the coefficient of friction and the normal force, which is equal to the weight of the runner. Once you have calculated the work done by friction, you can subtract it from the initial mechanical energy to determine how much energy is lost during the slide.

For the third question, you will need to use the formula for distance, which is d = v^2/2a (distance = velocity^2/2acceleration). In this case, the initial velocity is given as 4.0 m/s, and the acceleration is the coefficient of friction multiplied by the gravitational acceleration. Once you have calculated the acceleration, you can plug it into the formula along with the initial velocity to determine the distance the runner slides.

I hope this helps you understand the concepts and formulas better. Remember to always read the questions carefully and identify which formula you need to use before solving. Good luck with your studies!