biological or physical

1

Physics 1 2 hours Test #2 •Section 1: Short Answer. 1 mark each. REDUCE TO A CALCULATION. Answer questions in order. •Section 2: Long Answer. 10 marks each. Calculate full answers

2

Short Answer Section- Reduce to a calculation 1. Find the work done if a k=100 N/m spring originally stretched at x=2cm is extended to x=10 cm. 2. Find the work done on a 2kg mass if it experiences a force as shown

3. Find the final speed in Q2 of the 2 kg mass if it begins at rest. 4. A student lifts a 50 kg barbell 20 times in one minute. The barbell is lifted 75 cm each repetition. Find the mechanical power. 5. In Q4, find the food energy used if the student’s muscles are 20% efficient. 6. Write a work-energy equation to find the work done by the rocket engine if the rocket (mass m) starts at rest on the earth’s surface and ends up at altitude h moving at speed v 7. Find the period of oscillations if a 2kg mass is on a 50 N/m spring. 8. A mass in SHM is left of equilibrium and moving right. Sketch x-t and v-t graphs. 9. A 4 kg mass as in SHM on a 100N/m spring. Initially it is at the equilibrium point, moving right at 5 m/s. Find x(t). 10. A 25 kg mass falling at 8 m/s lands on a trampoline (k=1200 N/m). Write the equation to find how far the elastic material stretches in stopping the mass momentarily. 11. A mass is in simple harmonic motion according to x(t) = 0.25 cos(3t+0.25). What is its initial position and velocity? (be sure to include direction) 12. Using the axis provided, find the co-ordinate of the centre of mass

3

13. Write conservation equations for this oblique collision

14. Write momentum and restitution equations for this e=0.4 collision.

15. A 50 gram blob of putty moving at 25 m/s horizontally strikes and sticks to a stationary 4 kg pendulum bob, which swings up to height ‘h’. Which equations would you use to find h?

16. Find the heat energy required to heat 1.5 kg of water from 20°C and boil it completely into steam. 17. If we add 20 kg of steel at 120°C to 5 kg of water at 20°C, write the equation used to find the final temperature, T. 18. Find the rate of heat conduction through a 10 cm radius, 1 cm thick steel pot full of boiling water which sits on a 250°C stove-top burner. 19. Write the equation used to find the wind chill temperature if a 1.5m2 person with 34°C skin temperature goes outside on a h=15 Wm-2°C-1 , 5°C day (assume h=10 for still air) 20. Find the rate of radiant cooling if a 30°C object with 3 m2 of e=0.82 surface is cooling in a 20°C room.

4

Physics 1 Formulas constants: water r=1000 kg/m3 blood r = 1050 kg/m3 air r =1.29 kg/m3 mercury r= 13 600 kg/m3 1 atm= 760 mm Hg = 101 325 Pa = 14.7 psi I0= 1 ´ 10-12 W/m2 1 m3 = 1000L sphere surface area=4pr2 sphere volume=4/3pr3 fluids

r= M V P=

F A P = P0 + rgd = P0 + Pgauge

Fb = rgV Rv= Av)1 = Av)2 = V t Rm= r Rv

1 2 rv

2 + rgh + P)i + = 1 2 rv

2 + rgh + P)f DP = 8h L RV pr4

Fd=6p h r v Fd= ½ CD r A v2 waves y=f(x ± vt) y=Acos(kx-wt) = Acos k(x-vt) v= T/µ µ= M/L v=331+0.6T v=d/t =lf=w/k l=2p/k T=2p/w=1/f ln = 2L/n ln = 4L/n

P = 1 2 µ (wA)

2 v DP=rAvw b = 10 log(I/I0)

I = 1 2 r (wA)

2 v I = ! "#$!

f' = f v ± vo v ± vs

beat f = |f1 - f2| Dpath = nl Dpath= (n+0.5)l Oscillations

F=kx w= k m T=2p/w=1/f

vmax= Aw amax=Aw2 x= A cos(wt + d) v= = - Aw sin(wt + d) a=- = Aw2 cos(wt + d) Mechanics vf = vi + at Fnet = ma Fg=mg

vavg = vf + vi 2 d = vavg t Ff = µ FN µs,max ³ µk

d = vit + 1 2 at

2 a= v2 r v=

2pr T

vf2 = vi2 + 2ad F = kx

5

Work , Energy, Momentum

W=F d cos(q)= DE Wtot = KEf - KEi

P= W t = F vavg foodE= W+ Q Ei + Wnc = Ef

PEg = mgh PEs = 1 2 kx

2 KE= 1 2 mv

2

p=mv Fnet Dt = Dp = m(vf-vi)

m1v1 + m2v2 = m1v1 + m2v2 e = v2f-v1f v1i-v2i

x = S mixi S mi

y = S miyi S mi

Heat Q = m C DT Q = mL RQ= Q/t = kADT/d

Q/t = seA(To4 - Ts4) s = 5.67 ´ 10-8 J/(sm2K4) specific heats in J/(kg°C): water= 4186 ; ice= 2090; iron/steel = 450; steam=1520 ; body = 3500 latent heats: Lfusion (water) = 334 000 J/kg Lvap (water) = 2 256 000 J/kg

thermal conductivities: kair = 0.03 J/(s°Cm) ksteel= 80 J/(s°Cm) kglass= 0.84 J/(s°Cm) Rotation t = F^r= Fr^ w= Dq/t v=rw

aq=ra ar= v2 r

wf = wi + at Dq=wit + 1 2 at

2 wf2=wi2+2aDq

T= 1 f =

2p w Inew = Icm+md

2

I=S mr2 disk I = 12 mr 2 hoop I = mr2

sphere I = 2 5 mr

2 rod-end I = 1 3 mL

2 rod-mid I = 1 12 mL

2

tnet= Ia KE = 1 2 Iw

2 L = mrv)^ = I w

W=tDq P=W/t = tw

η = W

foodE