Physics

• bonkysleuth

  28 Jun 09, 22:38

  1 Two forces act at a single point as shown. What is the magnitude of the resulting force?

  

  I got 15N through vector diagram method. WIll anyone show me the theory working?

   

  2 In the figure below shows the profile of a transverse wave which is moving towards your right. What is the position of Q after a quarter of a period?

  

  I know how to find position at next instant but quarter of a period is stranger to me.

   

  3 A point light source is placed in a liquid of refractive index 1.25. It is found that rays from the source leave the liquid surface through a circular area of radius 12.0cm . What should be th depth of the source below the liquid surface?

  A 9 .0 cm    B 15.0 cm   C 18.0 cm    D 32.0cm

   

  4 A man stands between 2 cliffs as shown in the diagram and claps his hands once. Assuming velocity of sound in air is 320m/s, what will be the time interval between the 2nd and 3rd echoes?

  

  I got 0.625 secs but i am not sure if it's correct

  5 What is the effect on the readings on the ammeter A and voltmeter V on closing the switch S in the diagram?

  

  For me I think ammeter reading increases while that of volteter also increases. Or does voltmerer reading remain unchanged?

  6 All lamps in this circuit are rated 12V, 36W/ A,B,C, and D are 5 A fuses. Which fuse will melt when switch is closed?

  

  My answer is B

   

  If there's any mistake, feel free to explain to me. Hmmm, as for those questions i am not sure of, i'd need the help of you guys. thanks

• wishboy

  29 Jun 09, 20:37

  Q1.

  resolve both the forces into the horizontal and vertical components

  taking right direction as +ve : horizontal resultant force = 18 cos 25° - 12 cos 31° = 6.0275 N to the right

  taking upwards as +ve : vertical resultant force = 18 sin 25° + 12 sin 31° = 13.787 N upwards

  using pythagoras theorem, magnitude of resultant force = sqrt(6.0275² + 13.787²) = 15 N