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3 years ago

Please help I’m so desperate I’m giving about all my points

Physics

1 answer:

alexira [117]3 years ago

7 0

Answer:

1 and 5

Explanation:

potential energy is movement energy, and at 1 and 5 there is a lot of kinetic energy (built up energy) and not a lot of potential energy

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A child's top is held in place upright on a frictionless surface. The axle has a radius of ????=3.21 mm . Two strings are wrappe

tekilochka [14]

Answer:

Angular momentum, $L=6.47\times 10^{-3}\ m$

Explanation:

It is given that,

Radius of the axle, $r=3.21\ mm=3.21\times 10^{-3}\ m$

Tension acting on the top, T = 3.15 N

Time taken by the string to unwind, t = 0.32 s

We know that the rate of change of angular momentum is equal to the torque acting on the torque. The relation is given by :

$\tau=\dfrac{dL}{dt}$

Torque acting on the top is given by :

$\tau=F\times r$

Here, F is the tension acting on it. Torque acting on the top is given by :

$\tau=2F\times r$

$2T\times r=\dfrac{L}{t}$

$L=2T\times r \times t$

$L=2\times 3.15\times 3.21\times 10^{-3}\times 0.32$

$L=6.47\times 10^{-3}\ m$

So, the angular momentum acquired by the top is $6.47\times 10^{-3}\ m$ . Hence, this is the required solution.

7 0

4 years ago

Which is true about a concave mirror? Incident rays that are parallel to the central axis are dispersed but will be perceived as

Reil [10]

Answer:

'Incident rays that are parallel to the central axis are sent through a point on the near side of the mirror'.

Explanation:

The question is incomplete, find the complete question in the comment section.

Concave mirrors is an example of a curved mirror. The outer surface of a concave mirror is always coated. On the concave mirror, we have what is called the central axis or principal axis which is a line cutting through the center of the mirror. The points located on this axis are the Pole, the principal focus and the centre of curvature. The focus point is close to the curved mirror than the centre of curvature.

During the formation of images, one of the incident rays (rays striking the plane surface) coming from the object and parallel to the principal axis, converges at the focus point after reflection because all incident rays striking the surface are meant to reflect out. All incident light striking the surface all converges at a point on the central axis known as the focus.

Based on the explanation above, it can be concluded that 'Incident rays that are parallel to the central axis are sent through a point on the near side of the mirror'.

5 0

3 years ago

A pole-vaulter is nearly motionless as he clears the bar, set 4.2 m above the ground. He then falls onto a thick pad. The top of

Inessa05 [86]

initial height of the pole vaulter = 4.2 m

height of the pole vaulter just before it touch the pad = 80 cm

so the total displacement of pole vaulter just before he will touch the pad = 4.2 - 0.80 = 3.4 m

now by kinematics

$v_f^2 - v_i^2 = 2a d$

$v_f^2 - 0^2 - 2* 9.8*3.4$

$v_f^2 = 66.64$

$v_f = 8.16 m/s$

now after this he will come to rest after compressing the pad by 50 cm

so again we can use kinematics to find its acceleration

$v_f^2 - v_i^2 = 2 a d$

$0 - 8.16^2 = 2*a*0.50$

$a = -66.64 m/s^2$

so here its acceleration will be - 66.64 m/s^2

4 0

3 years ago

Chemicals in the air can combine with rain to produce acid rain, which is harmful to the environment. Which of these is most lik

irinina [24]

Hi there!

Normal rain has a pH between 5.0 and 5.5, which is slightly acidic on the pH scale. Acid rain on the other hand has an average pH of 4.0, much more acidic than your average rain.

Therefore, the most likely pH of acid rain would be 4.0.

7 0

3 years ago

Reflection of the images example

NISA [10]

Answer:

reflection of water ,sound and water waves etc

8 0

3 years ago