# Work Energy and Power - Online Test

Q1. The scalar product of two vectors A and B is
Answer : Option C
Explaination / Solution:

Scalar product means dot product and dot product of 2 vectors gives a scalar , example dot product of force and displacement gives work which is scalar

Q2. The scalar product of two vectors A and B in terms of the magnitudes and angle  is
Answer : Option A
Explaination / Solution:

The scalar product of two vectors can be constructed by taking the component of one vector in the direction of the other and multiplying it times the magnitude of the other vector. This can be expressed in the form

Q3. The scalar product of two vectors A and B in terms of the projections of the vectors on the x, y and z axis is
Answer : Option C
Explaination / Solution:

A = Ax i+ Ay j+ Azk

B = Bx i+ By j+ Bzk

A. B = (Ax i+ Ay j+ Azk). ( Bx i+ By j+ Bzk)

A. B = AxBx + AyB+ AzBz

Q4. The scalar product of vectors is
Answer : Option C
Explaination / Solution:

Scalar product is

a) Commutative:

b) Distributive

Q5. The change in kinetic energy of a particle is equal to the
Answer : Option A
Explaination / Solution:

if a body of mass m move with velocity u under the action of force F. Its velocity become v after displaced by s. then v2=u2+2as v2−u2=2as mv2−mu2=2mas 12mv2−12mu2=Fs Kf−Ki=W ΔK=W

Q6. The work done by the force is defined to be
Answer : Option C
Explaination / Solution:

Work done is given by

W = (Fcos)d

here Fcos is the component of applied force  in direction of displacement and d is magnitude of displacement.

Q7. If F is a force and d is the displacement in the direction of force then the work done by the force is given by
Answer : Option C
Explaination / Solution:

Work done = force in the direction of displacement multiplied by displacement

Q8. In which case is the work done zero?
Answer : Option D
Explaination / Solution:

Work done is given as

W = Fdcos

Here  is the angle between F and d  if both are perpendicular  then  = 90 degree so cos = 0  and thus work done is 0 .

Q9. The S.I unit of force is
Answer : Option A
Explaination / Solution:

In International System of Units (SI) the newton is the unit for force. It is equal to the amount of net force required to accelerate a mass of one kilogram at a rate of 1 m/sec2 in direction of the applied force. It is named after Isaac Newton in recognition of his work on classical mechanics, specifically Newton's second law of motion.

Dyne is a  cgs unit of force. One dyne is equal to 10−5 N

Q10. In a graph of F(x) vs x, the area under the curve
Answer : Option D
Explaination / Solution:

Work done by a variable force is given by W = ∫F(x)dx above integration gives us area area under F and x.