Class 9 Physics - MCQ Test (15-02-2017) - Class 9 MCQ

The potential energy of a freely falling object decreases progressively due to decrease in height. Kinetic energy is converted into heat and sound energy when a freely falling object on reaching the ground. Work is done only when change in position occurs.

The total energy of the system is always conserved. It is just transformed from one form to other form. Mechanical energy of a system is not conserved. It is converted into other form of energy.

The equation of motion for free fall can be used in case of falling of body only due to gravitation of earth without any other force. So, this statement is not true.

Pressure = force/ area. Here, Force = 200N. Area=5m². So, pressure = 200N/5m² = 40 Pa.

The force always occurs in pairs. According to third law of motion, there is equal and opposite reaction. So two force, action and reaction acts in pair always.

Rocket moves forward according to newton’s third law of motion. The gas and other substance coming out from the tail push the rocket in forward direction. Newton’s laws are universal.

A body can have zero velocity and still be accelerated or constant speed and still have varying velocity but a body cannot have a constant velocity and varying speed.

When a body changes its position with time, it is said that body is in motion. A body cannot be at rest and in motion at the same time. So, statement is false.

Ultrasound waves vibrate at frequency higher than 20,000Hz. Ultrasonic waves are directed towards kidneys.These waves with such a high vibration break the stones into tiny pieces so they can pass out of the kidney with the urine.

The eardrum is a stretched membranous structure at the junction of outer ear and middle ear. Vibration of eardrum causes production of sound that we hear. It is also known as tympanic membrane.

When you compress a coil spring you do work on it. The elastic potential energy increases.

The gravitational force of the earth on a satellite along a circular path is O as gravitational force of earth acts on right angle which is O for cos.

The weight of the body is the measure of force by which earth attracts the body. Acceleration due to gravity is less in case of poles and colour of bears found in these regions are white, called as polar bear.

Frictional force always opposes relative motion between the surfaces of contact. The direction of force is always in opposite direction.

When body is dropped from height, the potential energy deceases and kinetic energy increases. A ball dropped from height will conserve only kinetic energy.

A body moving horizontally with acceleration in vertical direction. A body moving with constant acceleration but zero velocity but a body moving with a constant velocity will not have accelerated motion.

A body moving with uniform motion, never changes it speed. So, the velocity of the body remain same after 10 second that is 10m/s.

Human beings are ultrasound deaf as humans are not able to hear frequency of sound above 20,000 Hz.
Ultrasound travels through various media including gases, liquids and solids, but cannot travel through a vacuum. The speed of sound varies by the medium it travels through. Sound is likely to travel faster through solids, followed by liquids and gases.

Cochlea, semicircular canals and auditory nerve are associated with inner ear.The internal ear contains colchea.The vibrating bones pass their vibrations to the colchea.The sensitive hair cells present in the colchea respond to the sound vibrations recieved and change them into nerve impulses.These impulses are then carried by the auditory nerves to the brain.

Potential energy of a spring increases when it is in the state of expansion and compression. Elastic potential energy increases with compression and gravitational potential energy increases on expansion.

Displacement is the shortest distance between initial and final position of the body. Displacement may be due to acceleration due to gravity during free fall.

Acceleration due to gravity (g) on moon is 1/6^th of the acceleration of gravity (g) on earth. So, weight of body of 10N on the surface of moon will be 1/6×10N = 1.67N.

The upward force experienced by the body when partially or completely submersed in fluid.

The two forces acting on same body, which are equal and opposite direction forms action and reaction. This is the newton’s thirds law of motion.

The velocity of the body falling towards depends upon gravitational force acting on it. So, both the body of masses 1 kg and 5 kg will have same velocity at particular height and fall at same time at the ground.

Distance travelled by a moving body can never be zero and negative.

Animals like dolphins,bats and tortoises produce sounds of frequency higher than 20000 Hz known as ultrasonic sounds.

Wave motion is a periodic disturbance in the medium produced by vibrating body. These disturbance moves into medium to produce sounds. Wave motion is also known as propagation of disturbances.

Sonar stands for Sound navigation and ranging. Sonar is a device that is used to find the depth of the sea,or to locate underwater objects like enemy's submarine,sunken ships,shoal of fish,etc.