Which item in the photo is a good thermal insulator, and why?

A 1000 kg car is rolling slowly across a level surface at 1m/s, heading toward a group of small innocent children.

Ne4ueva [31]

Answer:

The force is -1620.73 N.

Explanation:

Given that,

Mass of car = 1000 kg

Velocity = 1 m/s

Distance = 2 m

Angle = 30°

We need to calculate the force

Using formula of work done

$W_{net}=K_{f}-K_{i}$

$F\times d=K_{f}-K_{i}$

$Fd\cos\theta=-K_{i}$

$F=\dfrac{-K_{f}}{d\cos\theta}$

$F=-\dfrac{\dfrac{1}{2}mv^2}{d\cos\theta}$

Put the value into the formula

$F=-\dfrac{\dfrac{1}{2}\times1000\times(1)^2}{2\times\cos30}$

$F=-1620.73\ N$

Hence, The force is -1620.73 N.

7 0

4 years ago

Read 2 more answers

The displacement in simple harmonic motion is a maximum when the 1. velocity is a maximum. 2. kinetic energy is a maximum. 3. ve

dlinn [17]

Answer:

3. velocity is zero.

Explanation:

The velocity of a simple harmonic motion is given by

$v = \omega\sqrt{A^2-x^2}$

Here, ω is the angular velocity, A is the amplitude (or maximum displacement from the equilibrium point) and x is the displacement at any time.

At maximum displacement, x = A. Then

$v = \omega\sqrt{A^2-A^2} = 0$

Therefore, at maximum displacement, velocity is 0.

Practically, this can be observed in a simple pendulum. As it approaches the maximum displacement, its velocity reduces. It becomes zero at this point and then reverses as the pendulum changes course. Then the velocity begins to increase. It becomes maximum at the equilibrium point but once past that, the velocity begins to reduce as it approaches the other amplitude.

For acceleration,

$a = -\omega^2x$

It follows that at maximum displacement, the acceleration is a maximum. The negative sign indicates that it is in an opposite direction to the displacement. Both kinetic energy ( $\frac{1}{2}mv^2$ ) and linear momentum ( $mv$ ) are proportional to velocity; they are therefore both zero at the maximum displacement.

5 0

3 years ago

If a body accelerates from a state of relative rest in a gravity field, where does the energy come from to transfer as kinetic e

Delvig [45]

The energy that transforms into kinetic energy is the Potential Energy. It happens that objects can store energy as a result of its position. Image for example a slingshot. When you stretch the slingshot, it stores energy, this energy would be the energy you used to stretch the slingshot, the material aborbs it and then release to throw the projectile.

Now, on earth and everywhere in the universe where you are close to an object with mass, it exists a force called gravity that attracts you towards that object. Every object that has mass exercises gravitational attration towards the other objects. It just happens that Earth is has so much mass that its gravitational pull is way stronger that the gravitational pull of another object on its surface. This means things will tend to be as close as earth as possible, and in order to move something away from earth, you will have to perform a force in the opposite direction to Earth and, therefore, consume energy. This energy will be store as potential energy, and when you drop the object, the potential energy will be the energy that will transform to kinetic energy.

5 0

3 years ago

A pulley system has an efficiency of 74.2%. If you perform 200 J of work, how

Fudgin [204]

Answer:

C

Explanation:

If a pulley system has an efficiency of 74.2%, then only that fraction of the work performed will be useful. 74.2%=0.742. 0.742*200 is about 148J. Hope this helps!

8 0

3 years ago

Suppose you wish to whirl a pail full of water in a vertical circle at a constant speed without spilling any of its contents (ev

Yanka [14]

Answer:

V = 2.87 m/s

Explanation:

The minimum speed required would be that at which the acceleration due to gravity is negated by the centrifugal force on the water.

Thus, we simply need to set the centripetal acceleration equal to gravity and solve for the speed V using the following equation:

Centripetal acceleration = V^2 / r

where r is the distance of water from the pivot or shoulder.

For our case, r will be 0.65 + 0.19 = 0.84 m

and solving the above equation we get:

9.81 = V^2 / 0.84

V^2 = 8.2404

V = 2.87 m/s

6 0

3 years ago