Physics HELP

fukeneh

fukeneh

Active member
1. An elevator weighing 2.00 x 105 N is supported by a steel cable. What is the tension in the cable when the elevator is accelerated upward at a rate of 3.00 m/s2? (g = 9.81 m/s2)

2.A bullet with a mass of 6.00 g is fired through a 1.25 kg block of wood on a frictionless surface. The initial speed of the bullet is 896 m/s, and the speed of the bullet after it exits the block is 435 m/s. At what speed does the block move after the bullet passes through it?

3.Find the final equilibrium temperature when 10.0 g of milk at 10.0°C is added to 1.60 ´ 102 g of coffee with a temperature of 90.0°C. Assume the specific heats of coffee and milk are the same as for water (C pw=4.19J/G x C) , and disregard the heat capacity of the container.
 
Dont you just multiply gravity by the rate at which it is being pulled and then multiply the weight of the elevator? Its like a A x B x C type equation? I am not sure I took physics first semester last year
 
1.) F = ma

a = (gravity + upward accel) = (9.8+3)

F = Tension = (12.8*mass) (I forgot what the mass is, cause I can't read the post while writing.
 
2.) This is an elastic collision (I think... I'm assuming the bullet does not stick in the block)

m1*vbullet1 + m2*vblock1 = m1*vbullet2 + m2*vblock2

m1 = mass of bullet (once again I can't see what you wrote)

vbullet1 = initial speed before impact

m2 = mass of block

vblock1 = 0, as it was sitting still before getting hit

vbullet2 = exit velocity of bullet (400 some m/s?)

vblock2 = velocity of block after impact; solve for this.
 
3.) Even though I've taken mad physics and thermodynamics courses I forget the exact equation but you always end up multiplying mass * specific heat in that type of instance. Just google it, you'll find an identical problem somewhere.

sorry I'm so lazy, but I'm just about to go get drunk
 
1.i got to F=Tension=(12.8m/s^2*20394Kg)

just multiply them? and what would the units be?

2. i got 2212.8m/s

3. it is one of these answers

a. 85.3?C

b. 77.7?C

c. 71.4?C

d. 66.7?C
 
ehhh

its cool i dont have to turn it in till morning so hopefully something good will go down on here overnight
 
i haven't done any heat transfer for awhile but I got 82.86 celcius for #3. I used Q=m*c*delta t where q= heat in calories(9280 since its supposed to be water) and M is mass (112g) and c is specific heat of substance (1 g/degree C) and delta t is temp. This may or may not be right but its what I came up with.
 
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