Answer:
At the highest point the velocity is zero, the acceleration is directed downward.
Explanation:
This is a free-fall problem, in the case of something being thrown or dropped, the acceleration is equal to -gravity, so -9.80m/s^2. So, the acceleration is never 0 here.
I attached an image from my lecture today, I find it to be helpful. You can see that because of gravity the acceleration is pulled downwards.
At the highest point the velocity is 0, but it's changing direction and that's why there's still an acceleration there.
In Newton's third law, the action and reaction forces D.)act on different objects
Explanation:
Newton's third law of motion states that:
<em>"When an object A exerts a force on object B (action force), then action B exerts an equal and opposite force (reaction force) on object A"</em>
It is important to note from the statement above that the action force and the reaction force always act on different objects. Let's take an example: a man pushing a box. We have:
- Action force: the force applied by the man on the box, forward
- Reaction force: the force applied by the box on the man, backward
As we can see from this example, the action force is applied on the box, while the reaction force is applied on the man: this means that the two forces do not act on the same object. This implies that whenever we draw the free-body diagram of the forces acting on an object, the action and reaction forces never appear in the same diagram, since they act on different objects.
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Explanation:
Let us assume that forces acting at point B are as follows.

= 0 ...... (1)
= 0
= 0 .......... (2)
Hence, formula for allowable normal stress of cable is as follows.

T = 
= 3925 kip
From equation (1),
= -3925
= -3925
= 12877.29 kip
From equation (2), -12877.29 (Cos 60) + W = 0
= 0
W = 6438.64 kip
Thus, we can conclude that greatest weight of the crate is 6438.64 kip.
If you count the number of seconds between the flash of lightning and the sound of thunder, and then divide by 5, you'll get the distance in miles to the lightning: 5 seconds = 1 mile, 15 seconds = 3 miles, 0 seconds = very close. Keep in mind that you should be in a safe place while counting.