During that period of time, the bird's displacement was 4 km east. So its velocity was (4km east)/(11hrs). That's 0.36 km/hour east. (rounded)
Answer:
(a) A = m/s^3, B = m/s.
(b) dx/dt = m/s.
Explanation:
(a)

Therefore, the dimension of A is m/s^3, and of B is m/s in order to satisfy the above equation.
(b) 
This makes sense, because the position function has a unit of 'm'. The derivative of the position function is velocity, and its unit is m/s.
Answer:
D.
Explanation:
acceleration in the z component = velocity in z component / time. The question states velocity in z component is zero. Therefore, acceleration in z component = 0/time = 0.
Now the question does not specify whether the other velocity vectors (x or y) is zero or not. So its D.
Helium atom, in other words, it consistis of a particle having four protons and two neutrons.