Page 84 - Physics - XI

Sources of Error

1. Velocity of water jet may change as the pressure of water may not remain constant.
2. The water from jet may not strike the ground at a sharp point.

VIVA VOCE

Q1. What do you mean by projectile motion?
Ans. When a body is thrown at an angle with vertical, it moves in the space under the force of gravity
only. Its motion is called projectile motion.

Q2. What is the expression for horizontal range?
Ans. The horizontal range (R) is expressed as
2
R u sin 2
g
where u is the velocity of projection and θ is the angle of projection.

Q3. Defi ne time of fl ight.
Ans. The time for which projectile remains in motion is called time of fl ight.

Q4. Give expression for time of fl ight.
Ans. Time of fl ight (T) is given as
u 2sin
T
g

where u is the velocity of projection and θ is the angle of projection.
Q5. What is a projectile?
Ans. It is the name given to an object moving in space by itself without being propelled by any agent. The
only force which acts on an object is force of gravity.

Q6. Defi ne trajectory.
Ans. The path followed by a projectile is called its trajectory.
Q7. What is the shape of the trajectory of a projectile?

Ans. It is a parabola.
Q8. Defi ne the term horizontal range of the projectile.
Ans. The horizontal distance travelled by a projectile during its time of fl ight is called the horizontal
range of the projectile.

Q9. For what value of angle of projection θθ, the range R is maximum?
Ans. The range R is maximum for θ = 45° because R ∝ sin 2θ.

Q10. How are the two angles of projection for the same range related with each other?
Ans. The range is same for two values of angles, the angle and its complementary angle, i.e. their sum is
90°, i.e. θ and (90°– θ).

Q11. How would the range change if the velocity of projection is increased or decreased? (NCERT)

u sin
2
2
Ans. The horizontal range is given as, R R u 2
g
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