Answer:
a) 
b) 
Explanation:
Given the information from the exercise we can calculate the work done by the elevator using the following formula:
a) Considering you and your belongings as a system we know that the elevator is applying a Normal reaction force of:
Since the force applied and the displacement is in the same direction, the work done by the elevator is positive
b) The reaction force applied by the elevator is the same as the weight of the person
Since the force applied and the displacement is in opposite direction, the work done by the elevator is negative
I think the answer may be D- mechanical
Whenever an object is in projectile motion, that is, it has 2-dimensional motion in the x and y axis, the resultant force on the object is in the y-direction.
This is because once the object has been projected, or the ball has been kicked in this case, there is no longer a force being applied on it in the x-direction. The air resistance is also neglected so the ball's final velocity in the x-direction is equal to its initial velocity in the x-direction.
However, the force of gravity cannot be neglected and causes the ball to come downwards. Therefore, after the ball has been projected, the net force on the ball is downwards, due to gravity.
<span>a = (v2 - v1)/t= acceleration formula
a = (70 - 0)/7
a = 10 km/hr/sec
-----
It's better to use as few units as possible.
10 km/hr = 10 km*1000 m/km/(1 hr*3600 sec/hr) = 25/9 m/sec
a= 25/9 m/sec/se</span>
It depends how large the object is. But, if it is 2 by 4, most likely the wood sieges more than the glass.
Hope this helps.
