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Answer: (a)
Explanation:
Given
Mass of large truck is 4M with velocity V
Mass of small car is M which is at rest
After the collision car and truck stick together
Conserving momentum

For elastic collision, the velocity of the center of mass remains the same as the momentum is conserved and there is no acceleration involved.
So, for elastic collision velocity 
One factor that drives atmospheric circulation is the movement of air from warm equatorial areas to cooler areas.
This is true.
Burning wood would be the answer
Answer:
The difference between the velocity graph made walking at a steady rate means that its the same value in time, that means there's no slope on the graph, so its acceleration is 0
On the other hand, if the velocity is increasing with time, the slope of the graph becomes positive, which means that the acceleration of the particle is positive.