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3 years ago

7

A parachute on a racing dragster opens and changes the speed of the car from 85 m/sec to 45 m/sec in a period of 4.5 seconds. Wh

at is the acceleration of the dragster?

1 answer:

Serggg [28]3 years ago

6 0

Acceleration is change is velocity over time. So the change in velocity is 40 and time is 4.5 sec. So the acceleration is 40/4.5=8.89 m/s^2

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The length of a certain wire is kept same while its radius is doubled. what is the change in the resistance of this wire?

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The resistance of a wire is given by
$R= \frac{\rho L}{A}$
where $\rho$ is the resistivity of the material, L the length of the wire and A its cross-sectional area.

In the problem, $\rho$ and L remain the same, while A changes because the radius changes. The area is given by:
$A=\pi r^2$
This means that if we double the radius (2r), the area becomes
$A_{new}= \pi (2r)^2 = 4 \pi r^2 =4A$
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4 years ago

The perimeter of a sector of a circle is the sum of the two sides formed by the radii and the length of the included arc. A sect

snow_tiger [21]

Answer:

Length of the arc of this sector, l = 14 cm

Explanation:

It is given that, the perimeter of a sector of a circle is the sum of the two sides formed by the radii and the length of the included arc.

Perimeter of sector, P = 28 cm

Area of sector, $A=49\ cm^2$

According to figure,

2r + l = 28 ............(1)

Area of sector, $A=\dfrac{\theta}{360}\times \pi r^2$

Where, $\theta$ is in radian and $\theta=\dfrac{l}{r}$

Since, $1^{\circ}=\dfrac{\pi}{180}\ radian$

$A=\dfrac{l}{2\pi r}\times \pi r^2$

$r=\dfrac{98}{l}$

Put the value of r in equation (1) so,

$2\times (\dfrac{98}{l})+l=28$

$l^2-28l+196=0$

On solving above equation for l we get, l = 14 cm. So, the length of the arc of this sector is 14 cm. Hence, this is the required solution.

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3 years ago