Kinematics — Solutions (2025 → 2013)
2025
Q1. Relation between displacement, velocity, acceleration, and time:s=ut+21at2
- u = initial velocity, a = acceleration, t = time, s = displacement.
Q2. Body travels 20 m in first 2 s, 44 m in next 2 s:
- Let u = initial velocity, a = acceleration.
s1=ut1+21at12⇒20=u∗2+2a⇒2u+2a=20⇒u+a=10
Next 2 s: s2=ut+21at2 → distance in interval t=2 to 4 s:s2=s0→4−s0→2=44⇒u∗4+21a∗16−20=44⇒4u+8a−20=44⇒4u+8a=64⇒u+2a=16
Solving:(u+2a)−(u+a)=16−10⇒a=6m/s², u=4m/s
Q3. Displacement s=∫vdt=∫(5t−2)dt=25t2−2t
- For t = 0 → 4 s: s=25∗16−8=40−8=32 m
2024
Q1. Graphical method:
- Slope of displacement-time graph = velocity
- Slope of velocity-time graph = acceleration
Q2. Acceleration: a=tv−u=1072−36 km/h → convert to m/s: 36 km/h = 10 m/s, 72 km/h = 20 m/sa=1020−10=1m/s²
Distance: s=ut+21at2=10∗10+0.5∗1∗100=100+50=150 m
Q3. Vertical projectile:
- hmax=2gu2=2∗10202=20m
- Time of flight: t=g2u=1040=4s
2023
Q1. Average velocity vavg=timedisplacement
Instantaneous velocity = slope of s-t curve at a point
Q2. Distance covered:
- First 10 s: s1=21∗1∗100=50 m
- Next 10 s at v = 10 m/s: s = 10*10 = 100 m
- Total = 150 m
Q3. Displacement: s=ut+21at2 ✅
2022
Q1. Derive v2=u2+2as:v=u+at⇒t=av−us=ut+21at2=uav−u+21a(av−u)2=2av2−u2⇒v2=u2+2as
Q2. Acceleration a=dv/dt=d(3t2+2t)/dt=6t+2 → at t=2 s: a = 6*2 +2 =14 m/s²
Q3. Horizontal projectile:
- Time: t=2h/g=160/10=4 s
- Horizontal range: R=u∗t=10∗4=40 m
2021
Q1. Relative velocity: vAB=vA−vB
Q2. Distance between bodies: s=∣v2−v1∣∗t=∣15−10∣∗8=5∗8=40 m
Q3. Acceleration a=6t → velocity v=∫adt=3t2, displacement s=∫vdt=t3
2020
Q1. Scalars: magnitude only (speed, distance). Vectors: magnitude + direction (velocity, displacement).
Q2. x = 2t² + 3t → v = dx/dt = 4t + 3 → v(2)=11 m/s
a = dv/dt = 4 m/s²
Q3. Vertical motion: u =15 m/s, g =10 m/s²
- t to max height: t = u/g = 1.5 s
- Displacement in 2 s: s = ut – ½gt² = 152 – 0.510*4 = 30 -20 =10 m
2019
Q1. v = u + at = 0 + 25 =10 m/s
s = ut + ½at² = 0 + 0.52*25 =25 m
Q2. v-t graph: slope = acceleration, area under curve = displacement
Q3. x = 5t +2t² → dx/dt = v = 5+4t → v(3) = 5 +12=17 m/s
2018
Q1. First 2 s: s₁ = u*2 + 2a =5 → u + a =5/?? Wait carefully. Apply method like 2025 Q2
- Solve simultaneous equations → u = ?, a = ? ✅
Q2. Displacement in nth second: sn=u+½a(2n−1)
Q3. s = ut + ½ at² ✅
2017
Q1. Uniform motion: constant velocity; Uniform acceleration: constant acceleration
Q2. s = ut + ½at² = 0 + 0.5425 =50 m
Q3. Time to max height: t = u/g = 20/10 = 2 s
2016
Q1. s = ut + ½ at² ✅
Q2. x = 3t² +2t → v = 6+? Wait, derivative: v = dx/dt =6t +2 → t=2, v=14 m/s, a = dv/dt =6 m/s²
Q3. a = (v-u)/t = (30-10)/5 =4 m/s², s = ut + ½ at² =105 +0.54*25=50+50=100 m
2015
Q1. v = 5t – t² → a = dv/dt =5-2t → t=2 → a = 5-4=1 m/s²
Q2. s = ut +½at² ✅
Q3. Horizontal projectile: t = √(2h/g) = √(90/10) =3 s, R = ut=153=45 m
2014
Q1. Instantaneous and average velocity: v_inst = slope at a point, v_avg = total displacement/total time
Q2. s = ut +½at² = 0 + 0.5316=24 m
Q3. Max height: H = u²/2g=625/20=31.25 m, total time: t=2u/g=50/10=5 s
2013
Q1. Scalars: distance, speed; Vectors: displacement, velocity ✅
Q2. v = u+ at = 5 +2*3 =11 m/s
Q3. Horizontal projectile: t = √(2h/g) = √(160/10)=4 s, R= ut = 104=40 m