First Term Exam - Physics -Std 9 - Answer key

First Term Examination 2014

Answer Key – Physics Standard  9

1. Momentum
2. a. Greater massed body
   b. Increase the Mass, and Increase the Velocity
3. a. C-compressions , R- rarefactions
   b. Longitudinal wave
   c. Sound wave
4. a. 2 m
   b. 2 Hz
   c. 4 m
5. a. (i) t = 20 sec (ii) f = 0.5 Hz
   b. Period is inversely proportional to Frequency (when period increases frequency decreases)
   c. Length of the pendulum
6. a. The ball E move forward
   b. The balls E and D move forward
   c. Law of conservation of momentum
7. a. action =rowing on the lake, reaction = boat moves
   b. Newton's third law of motion
   c. Launching the rocket, Walking on the road
8. a. We can reduce the force acting on the hand.
   b. Rate of change of momentum increase, so the force also increase.
   When the time decreases, the value of ' change in momentum by time' increase.
9. a. take a suitable scale
   b. draw the graph
   c. time required = 12.5 seconds
10. a.Take a tray with water. Place some thermocol balls on the water. Fix a hacksaw blade on a stand and fix a pin on the other end of the hacksaw touching on the water. When the hacksaw blade vibrate , ripples formed in the water and thermocol balls move up and down.
    b. Waves are formed due to the disturbance in water. Particles vibrate perpendicular to the direction of the wave.
11. (A)
    a. F = ma
    acceleration a = F/m = 60/ 10 =6 m/s²
    b. final velocity v = u +a t = 0 + 6 x 2 = 12 m/s
    (B)
    a. velocity v = u + at = 0 + 10 x 3 = 30 m/s
    b. height = displacement s= ut + ½ at² = 0 x 3 + ½ x 10x 3 x 3 =45 m
12. a. (i) = 2G, (ii)= ¼ G
    b. Gravitational Constant
    c. decreases