Question

A and b go cycling in the same direction with speeds of 6 km/hr and 12 km/hr. A car from behind passes them in 9 and 10 seconds respectively. What is the speed of the car?

Answer 1

Explanation:

A and b go cycling in the same direction with speeds of 6 km/hr and 12 km/hr.

So, distance covered in one rotation is 2πr

= 2*3.14*21

= 131.88cm

Rpm =600

So

Distance covered in a minute

= 600*131.88

= 791.28m/min

Convert this to kmph

=(791.28/1000)/(1/60)

=47.5 kmph

Answer 2

$v_c=66\ km.hr^{-1}$ is the speed of the car

Explanation:

Given:

• speed of A, $v_a=6\ km.hr^{-1}$

• speed of B, $v_b=12\ km.hr^{-1}$

• time taken by the car to pass from A to B respectively, $t=1\ s$

The relative speed of B with respect to A:

$v_{ab}=6\ km.hr^{-1}$

Now the distance covered by this speed in 11th second:

$d=6\times \frac{11}{3600}$

$d=\frac{11}{600}\ km$

Now speed which car covered this distance:

$v_c=\frac{d}{t}$

$v_c=\frac{11}{600} \div \frac{1}{3600}$

$v_c=66\ km.hr^{-1}$

#learnmore

TOPIC: relative velocity

https://brainly.in/question/12106562