Answer:
tensional force
Explanation:
It usually exist in fluid or any liquid substance where by an object is put before it
e.g An ant can walk on water without submersed in it.
Answer:
(A) -2940 J
(B) 392 J
(C) 212.33 N
Explanation:
mass of bear (m) = 25 kg
height of the pole (h) = 12 m
speed (v) = 5.6 m/s
acceleration due to gravity (g) = 9.8 m/s
(A) change in gravitational potential energy (ΔU) = mg(height at the bottom- height at the top)
height at the bottom = 0
= 25 x 9.8 x (0-12) = -2940 J
(B) kinetic energy of the Bear (KE) =
=
= 392 J
(C) average frictional force = ![\frac{change in thermal energy}{height} = \frac{-(ΔKE+ΔU)}{h}](https://tex.z-dn.net/?f=%5Cfrac%7Bchange%20in%20thermal%20energy%7D%7Bheight%7D%20%3D%20%5Cfrac%7B-%28%CE%94KE%2B%CE%94U%29%7D%7Bh%7D)
- change in KE (ΔKE) = initial KE - final KE
- ΔKE =
-
- when the Bear reaches the bottom of the pole, the final velocity (Vf) is 0, therefore the change in kinetic energy becomes ΔKE =
- 0 = 392 J
\frac{-(ΔKE+ΔU)}{h}[/tex] =
=
= 212.33 N
<h2>
Answer: Positive acceleration</h2>
Acceleration
is the variation of velocity
over time
.
Now, it is said that a body has a <u>positive acceleration</u>, when the velocity of the body increases, that is, when the final velocity is greater than the initial velocity.
It is then said that it is an accelerated movement.
Answer:
(a) ![KE=16405.215 J](https://tex.z-dn.net/?f=KE%3D16405.215%20J)
(b) P = 6309.6981 W
(c) Value in above part is described as minimum because there would have been power loss in the actual system to achieve this acceleration from the state of rest.
Explanation:
Given:
mass of car, m = 1140 kg
expression of acceleration, ![a=1.14t-0.210t^2+0.240t^3](https://tex.z-dn.net/?f=a%3D1.14t-0.210t%5E2%2B0.240t%5E3)
where "t" is time in seconds
initial time, ![t_i=0 s](https://tex.z-dn.net/?f=t_i%3D0%20s)
final time, ![t_f=2.6 s](https://tex.z-dn.net/?f=t_f%3D2.6%20s)
(a)
We know,
![\frac{dv}{dt} =a](https://tex.z-dn.net/?f=%5Cfrac%7Bdv%7D%7Bdt%7D%20%3Da)
![dv=a.dt](https://tex.z-dn.net/?f=dv%3Da.dt)
![v=\int\limits^{2.6}_0 {1.14t-0.210t^2+0.240t^3} \, dt](https://tex.z-dn.net/?f=v%3D%5Cint%5Climits%5E%7B2.6%7D_0%20%7B1.14t-0.210t%5E2%2B0.240t%5E3%7D%20%5C%2C%20dt)
![v=5.3648 m.s^{-1}](https://tex.z-dn.net/?f=v%3D5.3648%20m.s%5E%7B-1%7D)
Kinetic Energy
∴![KE= \frac{1}{2} m.v^2](https://tex.z-dn.net/?f=KE%3D%20%5Cfrac%7B1%7D%7B2%7D%20m.v%5E2)
![KE=\frac{1}{2}\times 1140\times 5.3648^2](https://tex.z-dn.net/?f=KE%3D%5Cfrac%7B1%7D%7B2%7D%5Ctimes%201140%5Ctimes%205.3648%5E2)
![KE=16405.215 J](https://tex.z-dn.net/?f=KE%3D16405.215%20J)
(b)
We know,
Power
![P= \frac{\Delta KE}{\Delta t}](https://tex.z-dn.net/?f=P%3D%20%5Cfrac%7B%5CDelta%20KE%7D%7B%5CDelta%20t%7D)
![P=\frac{16405.215}{2.6}](https://tex.z-dn.net/?f=P%3D%5Cfrac%7B16405.215%7D%7B2.6%7D)
P = 6309.6981 W
(c)
Value in above part is described as minimum because there would have been power loss in the actual system to achieve this acceleration from the state of rest.
Answer:
Their kinetic energies have the same magnitude and sign.
Explanation:
Hi there!
Kinetic energy is not a vector, then it has no direction and therefore it does not matter the sense of movement of the car relative to a system of reference. Mathematically it would be also impossible to obtain a negative kinetic energy. The equation of kinetic energy (KE) is the following:
KE = 1/2 · m · v²
where m is the mass of the car (always positive) and v is its speed (not velocity, remember that the speed is the magnitude of the velocity vector, that´s why the kinetic energy is not a vector. I agree that the "v" in the formula is confusing).
So, even if we use a negative speed (that would be wrong), the kinetic energy will be positive because the speed is squared.
Then, if the cars have the same mass and speed, they will have the same kinetic energy, magnitude and sign (positive).