Physics Help?

Question

(1) How long does it take a 19 kW steam engine to do 6.8 X 10^7 J of work?

a) 1 hr

b) 2 hr

c) 30 min

d) 300 s

 

(2) What is the resultant of a vector that has components 25 m/s east, and 25 m/s north?

 

(3) If you were on the moon and fired a projectile, the maximum range you could achieve would occur with an angle of (in degrees)?

 

(4) A ball rolls down a hill with constant acceleration of 2.0 m/s^2 from rest. After 4.0 s, its velocity in m/s is?

Answer 1

Power = work/time

 

19 kW = 19000 watts , 1 w = 1 joule/second so 

19 kW = 19000 joule/s

 

19000 j/s = 6.8 x10^7 J/t Solve for time

 

t= 6.8x10^7J/19000J/s =  3579 s = 0.99 hours

 

resultant vector = squareroot(25^2+25^2) = sqrt(1250) = 25sqrt(2)

 

use range equation. The moons Gravity is 1/6 gravity on earth

 

v = at = 2(4) = 8 m/s