# CBSE Class 11-Physics: Kinematics Problems: Questions and Answers-Part 2

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**Question 1**:

A particle moves in a straight line according to the relation

Find the acceleration of the particle at displacement equal to zero.

**Solution**

We need to make use of differential calculus in such question. So, acceleration can be finding out like this

So, it is clear, we can find acceleration if we know the value of .

Now we need to find the value of t where .

So

so,

So, displacement becomes zero at these value of

Now acceleration can be finding out by the using the above derived equation

So, at

**Question:**

Which of the following remain constant during the motion of a projectile fired from a planet?

A) Kinetic energy

B) Momentum

C) Vertical component of velocity

D) Horizontal component of velocity

**Solution** (d)

Momentum

Since acceleration due to gravity acts during the motion, velocity of the body changes through-out the motion.

So and momentum changes

Now Acceleration due to gravity acts in vertical direction, so vertical component of velocity changes

Since there is no horizontal acceleration, horizontal components remain constant

**Graphical question**

Explain the acceleration during the motion