When astronauts are out in the space, either they communicate using radios or talk to one another by touching their helmets. Which of the following statements holds true about communication in space?
1.Sound is a vibration that cannot travel through vacuum.
2.Sound vibrations can travel through the material of the helmet to the other.
3.Radiowaves can travel through vacuum.
4.Helmets have speakers built in them which produce sounds when touched.
B2 and 3
C1, 2 and 3
D1 and 4
Nidhi pushed the plunger of syringe completely and dipped its needle in water. Then she slowly pulled the plunger while its needle was still immersed in water. Select the correct option regarding this.
A Water will move in the syringe when she pushed the plunger down due to air pressure.
B When she pushed the plunger down all the air moved out creating an empty space in syringe.
C Air outside the syringe exerted pressure on water causing it to move in when the plunger is pulled up.
D Both (B) and (C)
YEA IT IS C
The distance-time graph of motion of a cycle is shown in the figure. What is the average speed of cycle over a time period of 12 s?
A0.48 m s–1
B0.58 m s–1
C2.17 m s–1
D3.17 m s–1