Answer:
4th answer
Explanation:
The gradient of a distance-time graph gives the speed.
gradient = distance / time = speed
Here, the gradient is a constant till 30s. So it has travelled at a constant speed. It means it had not accelarated till 30s. and has stopped moving at 30s.
Answer:
f = 0.5 Hz
Explanation:
frequency = f
wave length = l
speed of wave = v
f = v/l → f = 3/6 = ½ = 0.5 Hz