Answer:
He could have many different hypothesis, but here is one.
Explanation:
If rubber bands are wider, then the rubber bands will stretch further, because the wider a rubber band is the stronger it is.
Answer:
-0.912 m/s
Explanation:
When the package is thrown out, momentum is conserved. The total momentum after is the same as the total momentum before, which is 0, since the boat was initially at rest.
where 
are the mass of the child, the boat and the package, respectively. 
are the velocity of the package and the boat after throwing.
Answer:
Power output is greater
Explanation:
The books mentioned are all identical and the to which these books are being lift up is same in both the slow and the fast process.
Now , we know that the work done is the scalar product of force applied and its displacement and displacement in both the cases is same. Thus the net work done is also same.
If we talk about Power, then power is work done per unit time. It includes the time which was absent in work done and also the time here is in inverse proportion to power. Thus slower process will take more time and less power while faster one will take less time and more power.
No, both the cars do not have the same velocity.
Velocity is a vector quantity and it is the rate of change of displacement with time or change in speed with direction.
Velocity has both magnitude and direction. So when you are in a car going 70 km/h and another car goes in the opposite direction at 70 km/h their velocities are different.
How?
Consider your car as moving in the positive direction, so its velocity will be 70 km/h and for the car moving in the opposite direction, since the direction is opposite, the velocity of that car will be -70 km/h. This is because, the velocity is a vector quantity that has both magnitude and direction. For one car, the direction is positive and for the other one the direction is negative.
