Question

Two cyclists start from the junction of two perpendicular roads, their velocities being $$3\,v\,m/minute$$   and $$4\,v\,m/minute.$$   The rate at which the two cyclists are separating is :

A. $$\frac{7}{2}\,v\,m/minute$$
B. $$5\,v\,m/minute$$  
C. $$v\,m/minute$$
D. None of these
Answer :   $$5\,v\,m/minute$$
Solution :
At time $$t,$$ the distance $$z$$ between the cyclists is given by $${z^2} = {\left( {3vt} \right)^2} + {\left( {4vt} \right)^2}$$
$$\therefore \,z = 5vt \Rightarrow \frac{{dz}}{{dt}} = 5v$$

Releted MCQ Question on
Calculus >> Application of Derivatives

Releted Question 1

If  $$a + b + c = 0,$$    then the quadratic equation $$3a{x^2}+ 2bx + c = 0$$     has

A. at least one root in $$\left[ {0, 1} \right]$$
B. one root in $$\left[ {2, 3} \right]$$  and the other in $$\left[ { - 2, - 1} \right]$$
C. imaginary roots
D. none of these
Releted Question 2

$$AB$$  is a diameter of a circle and $$C$$ is any point on the circumference of the circle. Then

A. the area of $$\Delta ABC$$  is maximum when it is isosceles
B. the area of $$\Delta ABC$$  is minimum when it is isosceles
C. the perimeter of $$\Delta ABC$$  is minimum when it is isosceles
D. none of these
Releted Question 3

The normal to the curve $$x = a\left( {\cos \theta + \theta \sin \theta } \right),y = a\left( {\sin \theta - \theta \cos \theta } \right)$$        at any point $$'\theta '$$ is such that

A. it makes a constant angle with the $$x - $$axis
B. it passes through the origin
C. it is at a constant distance from the origin
D. none of these
Releted Question 4

If $$y = a\ln x + b{x^2} + x$$     has its extremum values at $$x = - 1$$  and $$x = 2,$$  then

A. $$a = 2,b = - 1$$
B. $$a = 2,b = - \frac{1}{2}$$
C. $$a = - 2,b = \frac{1}{2}$$
D. none of these

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