Physics

Kinematics and Dynamics of Motion

128 Questions

Kinematics and dynamics explore projectile motion, inertia, free fall, and kinetic energy. These physics topics frequently appear in general science papers of major competitive exams. Practice these questions to understand the mechanical laws of motion.

Projectile motionFree fall calculationsInertia conceptsKinetic energyImpulse and collision

Kinematics and Dynamics of Motion Questions

Multiple choice physics propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

 A stone is dropped from the top of a tower $500$m high into a pond of water at the base of the tower. When is the splash heard at the top ? (Given $g = 10 ms^{-2}$ and speed of sound =$ 340 ms^{-1}$)

  1. $10s$
  2. $11.47s$
  3. $1.10s$
  4. $20s$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Given -  $h=500m   ,  g10m/s^{2} ,  v=340m/s$ ,

by ,  $h=ut+(1/2)gt^{2}$ ,
        $500=0+(1/2)10t^{2}$  ,   (initial velocity , $u=0$) ,
or     $t^{2}=1000/10=100$ ,
or     $t=10s$ ,
it is the time taken by stone to reach the water level , after that a sound is produced due to strike of stone on water , and sound travels upwards .Let t' be the time taken by sound to reach the base of tower ,
then , $t'=h/v=500/340=1.47s$ ,
therefore time taken by splash to hear at the top ,
        $T=t+t'=10+1.47=11.47s$

Multiple choice physics pressure in liquids and gases pressure dependence on force and area concept of pressure pressure on surface

1000 small balls each weighing 1 g strike one sq. cm of a area per second with a velocity of 100 m/sec in a normal direction and rebound with the same velocity. The pressure on the surface (in N/m$^2$) is :

  1. $2 \times 10^3$
  2. $4 \times 10^6$
  3. $10^7$
  4. $2 \times 10^6$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Force = change in momentum per second. For one ball, delta p = 2mv. For 1000 balls, F = 1000 * 2 * (0.001 kg) * (100 m/s) = 200 N. Area = 1 cm^2 = 10^-4 m^2. Pressure = 200 / 10^-4 = 2 * 10^6 N/m^2.

Multiple choice physics gravitation tides movements of ocean and sea water circulation of ocean water

A stone drop from height 'h' reaches at earth surface in 1 sec. If the some stone taken to moon and drop freely from height h then it will reaches at the surface of moon in the time:

  1. $\sqrt { 6 } sec$

  2. 9 sec
  3. $\sqrt { 3 } sec$

  4. 6 sec
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Using h = 0.5 * g * t^2, we have h = 0.5 * g_earth * (1)^2, so h = 0.5 * g_earth. On the moon, g_moon = g_earth / 6. Thus, h = 0.5 * (g_earth / 6) * t_moon^2. Substituting h, we get 0.5 * g_earth = 0.5 * (g_earth / 6) * t_moon^2, so t_moon^2 = 6, t_moon = sqrt(6).

Multiple choice physics turning effects of forces stability and centre of mass center of mass centre of mass

A football rolls through the ground. The path followed by center of mass of football is:

  1. linear

  2. circular

  3. rotational

  4. all the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When a football rolls through the ground, the path followed by center of mass of ball is linear as the center of mass remains always at a fixed height from the ground when the football rolls and moves in a straight line if the ball does not changes its direction of rolling which is assumed in this case.

The correct option is A.

Multiple choice maths equations and simple functions further equations solving linear equations with variable on both sides solution of linear equations in one variable

Neglecting air resistance, the upward velocity of the water in the stream of a particular fountain is given by the formula $v = -32t + 28$, where $t$ is the number of seconds after the water leaves the fountain. While going upward, the water slows down until at the top of the stream, the water has a velocity of $0$ feet per second. How long does it take a droplet of water to reach the maximum height?

  1. $0.825$ seconds
  2. $0.925$ seconds
  3. $0.875$ seconds
  4. $0.975$ seconds
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Given, $v = -32t + 28$
It is mentioned that at the maximum height, the velocity of water is $0$ feet per second.
Therefore, final velocity $(v) = 0$. 
$\Rightarrow 0=-32t+28$

$\Rightarrow 32t=28$      
$\Rightarrow t=\cfrac { 28 }{ 32 } =0.875$ seconds

Multiple choice physics force and types of force introduction to force what is force? concept of force and its unit

A ball of mass $400 \ gm$ is dropped from a height of $5 \ m$. A boy on the ground hits the ball vertically upwards with a bat with an average force of $100 N$ so that it attains a vertical height of $20 \ m$. Find the time for which the ball remains in contact with the bat.

  1. $0.12 s$
  2. $0.24 s$
  3. $0.36 s$
  4. $0.48 s$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$M=0.4 gm$ $=0.4 kg$

${h _1} = 5\,m$ $,$ ${h _2} = 20\,m$
$g = 10 \,m/{s^2}$
Velocity of the ball after dropping $5m:u$
Velocity of the ball after being hit by the bat$:v$
${u^2} = 2g{h _1} ; u = \sqrt {\left( {2 \times 10 \times 5} \right)}  = 10\,m/s\,\left( {downwards} \right)$

${v^2} = 2g{h _2} ;  \left( {2 \times 10 \times 20} \right) = v = 20\,m/s\left( {upwards} \right)$

Change of momentum $=$impulse$=$ $m(v+u)=12\,kg\,m/s$
Force$=100N=12/t$
$t=$ time of contact $=0.12sec$
Hence,
option $(A)$ is correct answer.

Multiple choice physics the essence of change forms of energy and energy conservation energy for everything forms of energy

A ball is dropped from $30\ m$ on hitting the ground if it loses $40$% of its energy, it rebounds to a height equal to

  1. $12\ m$
  2. $15\ m$
  3. $18\ m$
  4. $16\ m$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The initial potential energy of the ball is proportional to 30 m. Since it loses 40% of its energy upon hitting the ground, it retains 60% of its energy. The rebound height will therefore be 60% of the initial drop height, which is 0.60 * 30 = 18 meters.

Multiple choice modelling collisions collisions momentum work, energy and power physics

A ball is dropped on the floor from a height of $10m$. It rebounds to a height of $2.5\ m$. If the ball is in contact with the floor for $0.01\ s$, then the average acceleration during contact is nearly.

  1. $500\sqrt {2}m/s^{2} upwards$
  2. $1800\sqrt {2}m/s^{2} downwards$
  3. $1500\sqrt {2}m/s^{2} upwards$
  4. $1500\sqrt {2}m/s^{2} downwards$
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice modelling collisions collisions momentum work, energy and power physics

A ball of mass 0.20 kg falls freely from a certain height and rebounds elastically with a speed of $40 \,ms^{-1}$. The change in momentum of the ball is :

  1. $4\,kg \,ms^{-1}$
  2. $8\,kg \,ms^{-1}$
  3. $16\,kg \,ms^{-1}$
  4. $40\,kg \,ms^{-1}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Change in momentum, $\Delta p =- 2mv$
$= 2 \times 0.2\times 40 = 16 kg ms^{-1}$(magnitude)

Multiple choice physics force and newton's laws of motion first law of motion newton's first law of motion momentum and newton's laws

A rain drop of mass $0.1g$ is falling with uniform speed of $10{ cm/s }$. What is the net force the drop?

  1. ${ 10 }^{ -2 }N$
  2. ${ 10 }^{ -3 }N$
  3. $2\times { 10 }^{ -3 }N$
  4. $zero$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Uniform speed means that a body is traveling at a constant speed along a straight line. So it has no acceleration. Thus net weight $=ma=0$.

Multiple choice physics force and newton's laws of motion first law of motion newton's first law of motion momentum and newton's laws

A person sitting in an open car moving at constant velocity throws a ball vertically up into air. Where will the ball fall?

  1. Outside the car

  2. In the car ahead of the person

  3. In the car to the side of the person

  4. Exactly in the hand from which it was thrown up
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The ball has forward velocity equal to the velocity of the car even when ball is given velocity upwards.

So, the ball will cover the same distance as that by the car, and hence it will land in the hands of the person.

Multiple choice physics simple harmonic motion a few applications of linear shm simple pendulum example of simple harmonic motion

If a tunnel is cut at any orientation through earth, then in what time will, a ball released from one end, reach the other end (neglect the rotation of the earth) ?

  1. 84.6 minutes

  2. 42.3 minutes

  3. 8 minutes

  4. depends on orientation
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Force and to rque 
As we know
g depth = $g\left ( 1-\frac{d}{R} \right )$
$g _{d} = g\left ( \frac{R-d}{R} \right )\because (R-d)=x$
$g _{d}=\frac{g}{R}x$
$F _{r}=-mg _{d}$
$F _{R}=\frac{-mgx}{R}\Rightarrow F = -KX$
$T = 2\pi \sqrt{\frac{m}{k}}\rightarrow $ As we know
$K = \frac{mg}{R}$
$T= 2\pi \sqrt{\frac{mR}{mg}}$
$T= 2\pi \sqrt{\frac{R}{g}}$
$T = 84.6 ,minutes $
$A\rightarrow B;t=\frac{T}{2}=\frac{84.6}{2}=43.2$
Multiple choice physics study of sound reverberation applications of reflection of sound multiple reflection of sound and reverberation applications of ultrasound

A stone is dropped from the top of a tower of $125m$ high into a pond which is at base of the tower. When will the splash be heard at the top? (Given $g = 10ms^{-1}$ and speed of sound $=340ms^{-1}.$)

  1. $5s$
  2. $0.36s$
  3. $5.36s$
  4. $2s$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Time to fall: h = 0.5 * g * t^2 -> 125 = 5 * t^2 -> t^2 = 25 -> t = 5s. Time for sound to travel up: t2 = h / v = 125 / 340 = 0.367s. Total time = 5 + 0.367 = 5.367s.

Multiple choice evs - i substances, objects and energy renewable resources alternative fuels and energy sources alternative sources of energy

A ball of mass 50 g is thrown upwards. It rises to a maximum height of 100 m. At what height its kinetic energy will be reduced to 70%?

  1. 30 m

  2. 40 m

  3. 60 m

  4. 70 m
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

By work energy theorem,

$U _i+K _i=U _f+K _f$
$0+K _i=mgh+0$
$K _i=(50\times10^{-3})(10)(100)J$
$K _i=50J$ $-(i$)
Now, we have $K _f=\dfrac{70}{100}K _i$
By work energy theorem,
$0+K _i=mgh+\dfrac{70}{100}K _i$
$K _i-\dfrac{70}{100}K _i=(50\times10^{-3})(10)(h)$
$\dfrac{30}{100}K _i=0.5h$
From $(i)$, we have $K _i=50$
$h=2\times\dfrac{30}{100}\times50m$
$h=30m$