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zubka84 [21]
3 years ago
6

An object moving in a straight line is decelerating. Which about its acceleration is necessarily true?

Physics
1 answer:
Varvara68 [4.7K]3 years ago
3 0

Answer:

Its acceleration is certainly negative.

Explanation:

  • When an object moving in a straight line decelerates then its velocity certainly decreases.
  • Its acceleration is certainly negative.
  • As we know that acceleration is the rate of change in velocity and the object is decelerating i.e. its velocity is reducing with time.

a=\frac{v_f-v_i}{t_f-t_i}

where:

v_f\ \&\ v_i are final and initial velocities of the object

t_f\ \&\ t_i are final and initial time of observation.

  • Its SI unit is m.s^{{-2}
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Suppose that a steel bridge, 1000 m long, were built without any expansion joints. Suppose that only one end of the bridge was h
Stels [109]

Answer:

The difference in the length of the bridge is 0.42 m.

Explanation:

Given that,

Length = 1000 m

Winter temperature = 0°C

Summer temperature = 40°C

Coefficient of thermal expansion \alpha= 10.5\times10^{-6}\ K^{-1}

We need to calculate the difference in the length of the bridge

Using formula of the difference in the length

\Delta L=L\alpha\Delta T

Where, \Delta T= temperature difference

\alpha=Coefficient of thermal expansion

L= length

Put the value into the formula

\Delta L=1000\times10.5\times10^{-6}(40^{\circ}-0^{\circ})

\Delta L=0.42\ m

Hence, The difference in the length of the bridge is 0.42 m.

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Two uniform, solid cylinders of radius R and total mass M are connected along their common axis by a short, light rod and rest o
sveta [45]

Explanation:

A) To prove the motion of the center of mass of the cylinders is simple harmonic:

System diagram for given situation is shown in attached Fig. 1

We can prove the motion of the center of mass of the cylinders is simple harmonic if

a_{x} = -\omega^{2}  x

where aₓ is acceleration when attached cylinders move in horizontal direction:

<h3>PROOF:</h3>

rotational inertia for cylinders  is given as:

                                  I=\frac{1}{2}MR^{2} -----(1)

Newton's second law for angular motion is:

                                             ∑τ = Iα ------(2)

For linear motion in horizontal direction it is:

                                             ∑Fₓ = Maₓ ------ (3)

By definition of torque:

                                               τ  = RF --------(4)        

Put (4) and (1) in (2)

                                       RF=\frac{1}{2}MR^{2}\alpha

                                       RF=\frac{1}{2}MR^{2}\alpha

from Fig 3 it can be seen that fs is force by which the cylinders roll without slipping as they oscillate

So above equation becomes

                                   f_{s}=\frac{1}{2}MR\alpha------ (5)

As angular acceleration is related to linear by:

                                          a= R\alpha

Eq (5) becomes

                                    f_{s}=\frac{1}{2}Ma_{x}---- (6)

aₓ shows displacement in horizontal direction

From (3)

                                              ∑Fₓ = Maₓ

Fₓ is sum of fs and restoring force that spring exerts:

                                  \sum F_{x} = f_{s} - kx ----(7)

Put (7) in (3)

                                  f_{s} - kx  = Ma_{x}[/tex] -----(8)

Using (6) in (8)

                               \frac{1}{2}Ma_{x} - kx =Ma_{x}

                                     a_{x} = \frac{2k}{3M} x --- (9)

For spring mass system

                                  a= -\omega^{2} x ----- (10)

Equating (9) and (10)

                                  \omega^{2} = \frac{2k}{3M}

\omega = \sqrt{ \frac{2k}{3M}}

then (9) becomes

                                a_{x} = - \omega^{2}x

(The minus sign says that x and  aₓ  have opposite directions as shown in fig 3)

This proves that the motion of the center of mass of the cylinders is simple harmonic.

<h3 /><h3>B) Time Period</h3>

Time period is related to angular frequency as:

                                   T=\frac{2\pi }{\omega}

                                  T = 2\pi \sqrt{\frac{3M}{2k}

                           

 

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What is Speed? the ability to rest the ability to rest the ability to minimize the time cycle of a given movement the ability to
Vinvika [58]

Answer:

Speed is a scalar quantity that refers to "how fast an object is moving." Speed can be thought of as the rate at which an object covers distance. A fast-moving object has a high speed and covers a relatively large distance in a short amount of time.

Explanation:

The formula for speed is speed = distance ÷ time. To work out what the units are for speed, you need to know the units for distance and time.

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