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Simora [160]
3 years ago
13

Question

Mathematics
2 answers:
IgorLugansk [536]3 years ago
7 0

Answer:

the time is 1.57 sec and the distance is 49.32mm

Step-by-step explanation:

Given that,

The angle is 180°

Angular velocity is 2rev/sec

The radius is 10mm

we are to find the time and distance traveled at that time

The formula is

θ = at

where t is the time,

a is the angular velocity

θ is angle in radian

so,

θ = 180° × π/180°

θ = π

= 3.14

Hence ,

θ = at

3.14 = 2t

t = 1.57sec

let the distance be xmm

\frac{1.57 \times 180^0}{360} = \frac{x}{20 \pi} \\\\0.785 = \frac{x}{20 \pi} \\\\x = 49.32mm

Therefore , the time is 1.57 sec and the distance is 49.32mm

Vlad [161]3 years ago
6 0

Answer:

a) 0.25 s

b) 15.71 mm

Step-by-step explanation:

Given:-

- The radius of the coin, r = 10 mm

- The angle swept by the coin, θ = 180°

- The frequency of ration of the coin, f = 2 rev /s

Find:-

How long will it take the coin to roll through the given angle measure at the

given angular velocity?

How far will it travel in that time?

Solution:-

- We will first determine the angular speed ( ω ) of the coin. That is the rate of change of angle swept. Mathematically expressed as:

                       ω = dθ / dt = 2*π*f

- Separate the variables:

                      dθ = 2*π*f . dt

- Integrate both sides.

                      ∫dθ = 2*π*f ∫ dt

                      θ = 2*π*f*t

- The time taken to sweep an angle of ( θ ) is:

                      t = θ / 2*π*f

Where, θ is in radians. 180° = π radians

- Plug in the values:

                     

                      t = π / 2*π*( 2 )

                      t = 1 / 4 = 0.25 s   ... Answer

- The tangential speed (v) of any point on the circumference of a coin is. Considering only rolling motion of the coin:

                    v = r*ω = 2*r*π*f

- The velocity of the any point on the rolling coin circumference would be:

                   v = 2*(10)*π*(2)

                  v = 40π mm/s

- Since we are considering the coin as a rigid body and not a point mass. We have to determine the velocity of the center of mass of the coin ( Vcm ).

- Consider a coin as a circle. The point of contact of the between the circle ( coin ) is called the center of instantaneous velocity.

- Then mark two horizontal velocity vectors. One starts at the center of mass of the coin ( pointing right ): Denote this as the velocity of center of mass ( Vcm ).

- Other one starts from top most point lying on the circumference of the circle, this vector should be longer than the one made at center of mass (pointing right ): Denote this as the tangential velocity ( v ).

- Now joint the heads of two vectors ( v and Vcm ) with the center of instantaneous velocity ( contact between coin and surface ). Now make a vertical line that starts the top most point passing through center of mass and ends at the center of instantaneous velocity.

- We will end up with two similar triangles. We will use the law of similar triangle and determine the velocity of center of mass ( Vcm ):

                       2r / r = v / Vcm

                       Vcm = v / 2

-  Evaluate the velocity of center of mass ( Vcm ):

                      Vcm = 40π / 2

                      Vcm = 20π  mm/s    

- Use the distance-speed-time relationship and determine how far the coin travelled ( s ) in the computed time in part a:

                      s = Vcm*t

                      s = 20π*0.25

                      s = 5π = 15.70796 mm

Answer: The distance travelled by the coin in the time interval of 0.25 seconds is 15.71 mm ( rounded to nearest tenth )

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