# Posts by brigid

Total # Posts: 31

Math
I don't understand how the derivative of tanx/x equals sec^2x/x. I got sec^2x/(-x^2) by the quotient rule. Can someone explain to me step by step please?

Math
Oh I see! Would you mind helping me with another? y=Tanx/X at X=Pi/4 find the equation of the normal to the curve.

Math
Find an equation of the line tangent to the graph of y=sinx+3 at X=pi. The answer key says y=-X+Pi+3 But I got y=-X+5. Where did the Pi even come from?

scocial studies
how did imperialism, nationalism and militarism lead to WW1

Physics
Thanks so much!

Physics
I have a to find the frequency of "30 m radio waves" that have a given velocity. My question is does the "30 m" refer to wavelength? I think it does but am wondering could it also be taken to refer to amplitude.

Physics
Thanks so much!

Physics
My problem is as follows: A 12 kg pail hanging on a rope is pulled up by a 1 HP motor. What's the max. speed the pail could have? Do I use the formula Power = force * velocity or am I way off track?

Physics
Thanks so much for clearing that up!

Physics
I'm trying to determine the specific heat of copper by experiment and I have a question about the change in temperature of the copper. If I take the copper out of boiling water at 100 deg. C and place it in water at 10 degrees C, the temp. of the water increases to 14 deg...

Physics
I'm stuck on this problem. "You mix 100 ml 60 degree C water with 100ml 20 degree C water. Find the final temperature" Changing 100 ml to .1kg, I set .1*4186*(60-final temp.) + .1*4186*(final temp-20)=0 but my t's cancel out. I know it would work if I set my ...

Physics
An 60kg athlete wants to jump over a 2 m bar. How fast must she go the moment her foot leaves the ground in order to get her centre of mass up so high? I set KE of jumper to PE at top of bar to get 6.26m/s. Am I on the right track?

Physics
Thanks. Thought so but my friend disagreed with me.

Physics
If a .3kg arrow is fired at 120m/s at a 30degree angle with the horizontal, how high is it at the top of its arc? I'm confused. Do I break up the x and y components of velocity or do I set initial KE + PE = KE (top of arc)+ PE (top of arc) to get 1/2(.3)(120)*2+ 0 = 0 +.3(...

Physics
Thanks so much.

Physics
My problem is as follows "A 3 kg brick is dropped from a height of 1.0 m onto a nail which is vertically stuck in a plank of wood. If the nail doesn't move in much, how much heat is produced in the system when the brick hits and sticks onto the top of the nail." ...

Physics
Thanks!

Physics
If a ball is being lifted at a constant speed, does this mean that acceleration is 0 and therefore F=ma=0 and therefore no work is done on the ball?

Physics
Thank you.

Physics
I'm having a problem understanding a question. "If a man exerts a 200N force while pushing a crate 5.0 m across a floor against a frictional resistance of 40N, how much energy was expended by the person pushing?" I can figure out work done on the box and those ...

Physics
Thanks!

Physics
Regading my question yesterday about the ball being caught by the man on the scales (Sun. 3:47), I'm now wondering if, to get the final weight on the scales I need to add the actual ball's mass of .50 kg AS WELL AS the force of the ball on the man to his original ...

Physics
Thank you so VERY much!

Physics
Hi again, Can anyone help me with the physics problem I posted earlier today (Sunday) at 3:47 p.m. I would really appreciate it!!Thanks!

Physics
Hi again, Can anyone please help me with the physics problem I posted at 3:47 p.m. today (sunday). I would really, really appreciate it. Thanks!

Physics
I've been stuck on this problem and hope someone can help me. A man is standing on scales which show his weight as 607.6 N. A .50 kg ball is dropped from a height of 1 m into his hands. His hands drop 25 cm from chest level to waist level during the catch.His mass is 62 kg...

Physics
Thanks!

Physics
Can someone please help me sort out this problem? "A boy standing at the equator jumps vertically into the air. Does he land in the exact same spot after landing?" I'm thinking that when he jumps he is also moving horizontally with the earth and so he will land ...

Physics
Yeah! thank you very much for checking my work. I can go to bed now.

Physics
Can someone please tell me if I've approached this homework problem correctly. A boy is running at his best speed of 6.0 m/s to catch a bus stopped at the lights. When he is 16 m from the bus, the light goes green and the bus pulls away at an acceleration of 1.0 m/s/s. ...