A box sliding on a horizontal frictionless surface encounters a spring attached to a rigid wall and compresses the spring by a c
1 answer:
Answer:
a) K = 49.5 J b) k = 1378 N / m c) ΔE = 34 J d) μ = 0.399
Explanation:
For this exercise we will use the concepts of energy
a) The initial kinetic energy is
K = ½ m v²
K = ½ 3.96 5²
K = 49.5 J
b) let's use energy conservation
Em₀ = K = ½ m v²
= Ke = ½ k x²
Em₀ =
½ m v² = ½ k x²
k = m v² / x²
k = 3.96 5² / 0.268²
k = 1378 N / m
c) Let's calculate the final energy of the spring
= Ke = ½ k x²
= ½ 1378 0.15²
= 15.5 J
The initial energy is the kinetics of the block
Em₀ = 49.5 J
The lost energy is the difference with the initial
ΔE = - Em₀
ΔE = 15.5 - 49.5
ΔE = - 34 J
the negative sign means that the energy dissipates
d) For this part we use the concept of work
W = F d cos θ = ΔK
In this case the force is the friction force that always opposes displacement, so the angle 180 ° and cos 180 = -1
W = -fr d = ΔK
The force of friction is
fr = μ N
With Newton's second law
N-w = 0
N = W = mg
Let's calculate
-μ mg d = Kf -K₀o
μ = K₀ / mgd
μ = 49.5 / (3.96 9.8 3.20)
μ = 0.399
You might be interested in
1) 26.2 m/s
The mechanical energy of the divers at any point of their vertical motion is sum of the kinetic energy and the gravitational potential energy:
where
m is the mass of the diver
v is the speed
g = 9.8 m/s^2 is the acceleration due to gravity
h is the height above the water
When the diver is on the cliff, v = 0 (he is at rest), so K=0 and the initial mechanical energy is just potential energy:
where h=35 m is the height of the cliff.
When the diver hits the water above, h = 0, so U=0 and the final mechanical energy is just kinetic energy:
since the total mechanical energy is conserved, we have
And solving the equation for v, we find the speed when they reach the surface of the water:
2) It is converted into thermal energy of the water
When the diver enters the water, he suddenly feels another force acting against the motion of the diver: the resistance of the water. The resistance of the water acts upward, slowing down the diver until he stops.
In this process, the speed of the diver (v) decreases, and therefore the kinetic energy of the diver decreases as well, until it becomes zero.
However, this does not mean that the conservation of energy has been violated. In fact, the kinetic energy of the diver has been converted into thermal energy of the molecules of water surrounding the diver.
Answer:
Explanation:
Given
Time period for both string is same
and tension in string 2 is twice the first string
Tension will provide centripetal acceleration
thus