The work done to pull the sister back on the swing is equal to the increase in potential energy of the sister:
(1)
where m is the sister's mass, g is the gravitational acceleration and
is the increase in altitude of the sister with respect to its initial position.
By calling
the angle of the chain with respect to the vertical, the increase in altitude is given by
(2)
where L is the length of the chain.
Putting (2) inside (1), we find
from which we can find the mass of the sister:
No because for example you get a brownie mix and you want to make them well you put all of the mixture in the blender and you finish making them. Well now the brownies are done. well are they still the brownie mix?
Answer:
book speed is 3.99 m/s
Explanation:
given data
mass m = 490 g = 0.490 kg
compressing x = 7.10 cm = 0.0710 m
spring constant k = 1550 N/m
to find out
book speed
solution
we know energy is conserve so
we can say
loss in spring energy is equal to gain in kinetic energy
so
..................1
put here value
v = 3.99 m/s
so book speed is 3.99 m/s
If you only know its speed, that's not enough information to catch it. You could even chase it at DOUBLE that speed, and you'd never catch it if you were chasing in the wrong direction.
You also have to know the DIRECTION the runaway car is going, so that you can chase in the same direction.
Now that you know its speed AND direction, you know its velocity. You need that information to have any chance of catching it.
