Answer:
a) 1.75s b) 17.2 m/s (down)
Explanation:
d1= 15m d2= 0m (because it hits ground)
a= -9.81 m/s^2 t=???
Equation
the triangle means change in so d2-d1
Δd= v1 * t + 1/2 * a * t^2
0m-15m= v1*t + 1/2 a t^2
-15 m= 0m/s*t (goes away) + 1/2* a *t^2
-15mx2= t^2
-15mx2/a= t^2
Square root (-30/-9.81m/s^2)
t=1.75 s
b) now v2!!
Im going to use v2= v1 + a*t
v2= 0m/s + -9.81 x 1.75s
v2 = -17.2 m/s or you can say 17.2 m/s down!!!
Answer:Learn what gravitational potential energy means and how to calculate it. ... a pulley and rope, so the force due to lifting the box and the force due to gravity, ... would be used by an elevator lifting a 75 kg person through a height of 50 m if the ... When you are close to a planet you are effectively bound to the planet by gravity ..
Explanation:
I'm sorry but I don't really understand the question. What is the quest actually asking???
Answer:
The only work done is when the person lifts the sack over a distance, W = 78.48 [N]
Explanation:
We have to remember the definition of work, which tells us that work is the result of a force by a distance, we must apply this concept in each of the movements of the person in the problem described.
W = F * d
where:
F = force [N]
d = distance [m]
The force is given by the producto of the mass by the gravity.
F = 5 * 9.81 = 49.05 [N]
W = 49.05 * 1.6 = 78.48 [N]
The general formula to calculate the work is:
where F is the force, d is the displacement of the couch, and 
is the angle between the direction of the force and the displacement. Let's apply this formula to the different parts of the problem.
(a) Work done by you: in this case, the force applied is parallel to the displacement of the couch, so 
and 
, therefore the work is just equal to the product between the horizontal force you apply to push the couch and the distance the couch has been moved:
(b) work done by the frictional force: the frictional force has opposite direction to the displacement, therefore 
and 
. Therefore, we must include a negative sign when we calculate the work done by the frictional force:
(c) The work done by gravity is zero. In fact, gravity (which points downwards) is perpendicular to the displacement of the couch (which is horizontal), therefore 
and 
: this means
.
(d) Work done by the net force:
The net force is the difference between the horizontal force applied by you and the frictional force:
And the net force is in the same direction of the displacement, so and and the work done is
