Physics Mock Test- 5 - Class 9 MCQ

Force is a push or a pull that changes or tends to change the state of rest or uniform motion of an object or changes the direction or shape of an object

Option C is correct.

The Kinetic energy acquired by an object that is acted upon by a force is equal to the work done by the force. The work done by the force is equal to the force times the distance the object moved against the force. Therefore, in this case the Kinetic energy acquired by the body is equal to 25 N x 10 m = 250 J.

When an object is at rest it will not be able to cover any distance . So for any object at rest the distance -time graph is horizontal to time axis

The commercial unit of energy is a kilowatt hour. 
One kilowatt hour is defined as the amount of electrical energy consumed when an electrical appliance having a power rating of 1 kilowatt is used for 1 hour.

Wave motion transfers energy from one point to another, often with no permanent displacement of the particles of the medium —that is, with little or no associated mass transport. They consist, instead, of oscillations or vibrations around almost fixed locations.

Sound is nothing more than a local disturbance whose propagation is facilitated by the collisions between particles; This disturbance propagates in a longitudinal wave; imagine one molecule hitting the another molecule, and then that molecule hitting the next molecules, and so forth.
The distance between molecules in solids are very small, i.e., solids are more dense - as compared to liquids and gases. Because they are so close, they can collide very quickly .i.e, it takes less time for a molecule of a solid to ‘bump’ into its neighbour. Solids are packed together tighter than liquids and gases, hence sound travels fast in solids. 

Vector quantity has both magnitude and direction but scalar quantity have only magnitude

2 D = velocity X time
D = (velocity X time) / 2 = 1450 X 4 / 2 = 2900 m = 2.9 km

• Distance is a scalar quantity that refers to "how much ground an object has covered" during its motion. 
• Acceleration is a vector quantity that is defined as the rate at which an object changes its velocity.
• Velocity is a vector quantity that refers to the speed of an object in a particular direction.

It vibrates, which, in turn, causes the air around it to vibrate. The vibration of air causes your eardrum to vibrate in tune with the vibrating air. This is interpreted by your brain as sound.

Another popular use for ultrasonics is in ships, both for navigation and for locating objects underwater. Sound travels faster through water than through air, which is very helpful because light hardly travels through water at all. Most people know that whales can use low-frequency sound to communicate across entire oceans. Submarinesuse a similar trick with a type of navigation called sonar (sound navigation and ranging), which is a bit like an underwater equivalent of radar.

We know, F = ma
F  =  5 * 5 
F =   25 
We, also know; 
W  =  F. s 
=   25 * 2 
W  =  50 J

Initial velocity ,u= 20 m/s. final velocity = o , g = 10ms⁻² . V = u + gt, 0 = 20+(−10)×t20+(−10)×t, t = 20/10 = 2s. time taken to fall in downward direction = 2s. hence total time taken = 2s +2s = 4s.

Correct Answer :- b

Explanation:- Force of gravitation is equal to product of masses divided by square of the distance between them. So, the force of gravitation between two bodies will be the same irrespective of their place. 

So, the ratio will be 1:1.

The acceleration mentioned is due to the force of gravity. This is a force of attraction based on the mass of an object and the distance between the two objects Newton's law of universal gravitation. Generally on the surface of the earth we treat this as 9.8 m/sec^2 or 32 ft/sec^2. The way that Einstein describes it is that mass curves spacetime, thus space itself is pushing down on the falling object and is the cause of the force. 

So option C is correct.

According to the law of inertia or Newton's first law of motion, a body in state of rest or of uniform motion remains in state of rest or of uniform motion unless it is acted upon by an external force. Hence a body in uniform motion required no force to keep them in uniform motion.

The Second Law of Motion states that if an unbalanced force acts on a body, that body will experience acceleration ( or deceleration), that is, a change of speed.

 One can say that a body at rest is considered to have zero speed, ( a constant speed). So any force that causes a body to move is an unbalanced force. Also, any force, such as friction, or gravity, that causes a body to slow down or speed up, is an unbalanced force. 

The value of universal gravitational constant (G) is6.67×10⁻¹¹Nm²/Kg²  Which is constant and independent of mass, distance between the bodies and other factors.

Sound needs a medium to be transmitted thus a person on the moon cannot hear another person on the moon. This is because there is no air on the moon and it is a vaccum thus there is no medium for sound waves to travel.

• It is Newton's third law of motion which states that every action has an equal and opposite reaction.
• So, every action and reaction forces are equal and in opposite direction.