Answer:
Please find the answer in the explanation
Explanation:
Friction is a force that opposes motion. One or two of the advantages of friction are break and ability of an object to walk.
Writing yes it is useful because when your writing because friction helps you see what your writing
ii. Rubbing. Yes, it is useful.
friction make it possible for two object to rub each other
iii. Skiing. No. It is not useful because With presence of friction, skiing will not be possible.
iv. Rotating a wheel No. It is not useful because Friction will oppose the rotation of the wheel.
F = net force acting on the elevator in upward direction = 3000 N
m = mass of the elevator = 1200 kg
a = acceleration of the elevator = ?
Acceleration of the elevator is given as
a = F/m
a = 3000/1200
a = 2.5 m/s²
v₀ = initial velocity of the elevator = 0 m/s
Y = displacement of the elevator = 15 m
t = time taken
Using the kinematics equation
Y = v₀ t + (0.5) a t²
15 = (0) t + (0.5) (2.5) t²
t = 3.5 sec
Answer:
(B) Dark energy does not exist and there is much more matter than current evidence suggests.
Explanation:
The repulsive force which is accelerating expansion of the universe is called as dark energy. Most of matter present in the universe is the dark matter of about eighty five percent.
So, a collapsing universe would not have the dark energy and there is more matter which is not the dark matter. This theory is rejected because expansion of the universe is observable.
Am sorry what can you be more specific
The force on a 64 k person decelerating on that rate would be :
F = ma
F = 64 kg x 30 x 9.8
= 18816 N
Hope this helps
