Physics (Class 8)
Class 8 physics covering motion, forces, optics, electricity, and gravitation
Questions
Choose the wrong statement.
- Distance is a scalar quantity.
- Displacement is a vector quantity.
- Accleration is a scalar quantity.
- Retardation is a vector quantity.
- Statement 1
- Statement 2
- Statement 3
- Statement 4
A stone which is tied to a thread is whirled in a circular path. As it revolves, the thread suddenly breaks. What happens then?
- The stone moves radially inward.
- The stone flies off tangentially.
- The stone moves radially outward.
- The stone falls straight down.
If the momentum of a body is doubled, the kinetic energy ___________.
- becomes halved
- gets doubled
- remains unchanged
- becomes fourtimes
The total force exerted by the body perpendicular to the surface called ________________.
- thrust
- pressure
- resultant force
- frictional force
If a solid sinks in water it means its relative density is _____________.
- lesser than unity
- equal to unity
- infinite
- greater than unity
Graphite powder is used in machine to ______________.
- enhance friction
- enhance the lustre
- reduce friction
- reduce efficiency
If we are talking about the change of displacement with time, we are referring to ________________.
- speed
- acceleration
- retardation
- velocity
The point from which the earthquake waves originate is called the _____________.
- epicentre
- seismic focus
- tectonic plates
- fault zones
Which of following statements is incorrect?
- Lightning is the heavy flow of charge between clouds and earth.
- Lightning enables nitrogen of the air to combine with oxygen to form oxides of nitrogen.
- It is safer to remain in open space or under a tree during lightning.
- Lightning enables ozone to be formed from oxygen.
When angle between the two mirrors is right angle and a candle is placed in the middle. How many images are formed?
- Infinite
- Three
- More than three
- Two
On rubbing two objects, a body acquires negative charge it means ________________.
- the body has acquired excess of protons
- the body has acquired excess of electrons
- the body has lost some electrons
- the body has lost some neutrons
The weight of an object is due to ________________.
- gravitational force
- frictional force
- both gravitational and frictional forces
- neither gravitational nor frictional force
Where is the image of an object formed by a plane mirror?
- On the surface of mirror
- Just in the front of mirror
- Just behind the mirror
- At double the distance behind the mirror
Which of the following statements does not explain the effect of force, which is greater when area of contact is smaller?
- We feel pain when we hold sharpen pencil between the index fingers of both hands and pressing it hard.
- Hammering a nail on a wall is easier than hammering a wooden piece.
- A rubber band on pulling becomes longer.
- Cutting an apple with a sharp edge is easier.
Why is one end of iron nail sharpened?
- To change the direction of force applied at the head
- To enhance the force applied
- To increase the magnitude of force applied at the head
- To increase the magnitude of pressure acting on an object
Friction has both advantages and disadvantages. In which case is friction a disadvantage?
- Applying brakes
- Writing
- Walking
- Running a machine
The pressure exerted by the liquid on an object immersed in it ________________.
- depends on colour of the liquid
- varies with change in temperature
- increases with increase in depth
- decreases with increase in depth
Why a body weighs less on moon than on earth?
- There is less force of gravity on moon.
- There is no atmosphere on moon.
- Moon is farther away from Sun.
- Moon has more gravitational force.
Fill in the blanks.
Force of friction is ___________for a rough surface.
Spilling oil on the rough surface _________the friction.
- small; increases
- small; decreases
- large; increases
- large; decreases
Momemtum is a vector quantity. It is a measure of _________________.
- weight
- mass
- quantity of motion
- velocity
When two bodies are rubbed, why are negatively charged particles transferred?
- Because they are in excess in an atom.
- Because they are loosely bounded.
- Both options 1 and 2 are true.
- Both options 1 and 2 are false.