Posts by Brigid
Total # Posts: 31
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.
May 19, 2009
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?
May 13, 2009
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...
May 7, 2009
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 ...
April 28, 2009
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?
April 19, 2009
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(...
April 16, 2009
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." ...
April 16, 2009
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 ...
April 7, 2009
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 ...
March 23, 2009
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...
March 22, 2009
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 ...
March 11, 2009
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. ...
March 4, 2009