Answer:
The average speed is 8.0 km/h
Explanation:
We use the data for the return journey to calculate the distance travelled using the constant velocity equation:
s = v t =6*4=24km
Note I didn't change any units so the answer comes out in kilometres.
Now use the distance and time taken to travel to Guam to find the average speed:
v=st=24/3=8.0km/h
Answer:
1) d
2) 5 m/s
3) 100
Explanation:
The equation of position x for a constant acceleration a and an initial velocity v₀, initial position x₀, time t is:
(i) 
The equation for velocity v and a constant acceleration a is:
(ii) 
1) Solve equation (ii) for acceleration a and plug the result in equation (i)
(iii) 
(iv) 
Simplify equation (iv) and use the given values v = 0, x₀ = 0:
(v) 
2) Given v₀= 3m/s, a=0.2m/s², t=10 s. Using equation (ii) to get the final velocity v:
3) Given v₀=0m/s, t₁=10s, t₂=1s and x₀=0. Looking for factor f = x(t₁)/x(t₂) using equation(i) to calculate x(t₁) and x(t₂):

Answer: Seismic waves arrive at a seismograph in the order of fastest to slowest:primary waves, secondary waves, surface waves.
Explanation: