Projectile Motion
Kinematics
42
JEE Qs
7%
Hard
90
min
Always resolve the initial velocity into horizontal and vertical components and analyze motion independently in these two perpendicular directions using 1D kinematic equations.
🧮 Key Formulas
✅ Key Points for JEE
- 1Projectile motion is a combination of two independent motions: uniform velocity horizontally and uniformly accelerated motion vertically under gravity.
- 2Horizontal component of velocity (Vx) remains constant throughout the motion, as horizontal acceleration is zero.
- 3Vertical component of velocity (Vy) changes due to constant downward acceleration 'g'. At the highest point, Vy = 0.
- 4The trajectory is symmetric about the highest point: time to reach maximum height equals time to fall from maximum height to the same horizontal level.
- 5For a given launch speed, the horizontal range is maximum when the projection angle is 45 degrees, and ranges are equal for complementary angles (theta and 90-theta).
⚠️ Common Mistakes
- ✕Confusing horizontal and vertical components of velocity and acceleration, or applying vertical acceleration 'g' to horizontal motion.
- ✕Incorrectly using sign conventions for displacement, velocity, or acceleration due to gravity, especially when motion is upwards then downwards.
- ✕Attempting to solve problems without resolving initial velocity into its horizontal and vertical components first.
📝 Practice Questions
See allQ27.A ball having kinetic energy KE, is projected at an angle of 60∘ from the horizontal. What will be the kinetic energy of ball at the highest point of its flight ? (1) (KE) (2) (KE) 8 2 (3) (KE) (4) (KE) 16 4
Q28.The velocity-time graph of an object moving along a straight line is shown in figure. What is the distance covered by the object between t = 0 to t = 4 s ? (1) 30 m (2) 11 m (3) 10 m (4) 13 m
Q50.A particle is projected at an angle of 30∘ from horizontal at a speed of 60 m/s. The height traversed by the particle in the first second is h0 and height traversed in the last second, before it reaches the maximum height, is h1 . The ratio h0 : h1 is _________ [Take, g = 10 m/s2 ]
Q43.The motion of an airplane is represented by velocity-time graph as shown below. The distance covered by airplane in the first 30.5 second is _______ km . (1) 12 (2) 3 (3) 6 (4) 9
Q27.The position vector of a moving body at any instant of time is given as →r = . The magnitude (5t2^i −5t^j)m and direction of velocity at t = 2 s is, (1) 5√15 m/s, making an angle of tan−1 4 with - ve (2) 5√15 m/s, making an angle of tan−1 4 with + ve Y axis X axis (3) 5√17 m/s, making an angle of tan−1 4 with + ve (4) 5√17 m/s, making an angle of tan−1 4 with - ve X axis Y axis
Q31.Two projectiles are fired with same initial speed from same point on ground at angles of (45∘−α) and (45∘+ α), respectively, with the horizontal direction. The ratio of their maximum heights attained is : (1) 1−tan α (2) 1−sin 2α 1+tan α 1+sin 2α (3) 1+sin 2α (4) 1+sin α 1−sin 2α 1−sin α
NCERT Chapters
- Class 11 Physics Ch 4: Motion in a Plane