Class 8 Science · Original EZT practice
Exploring Forces (Class 8 Science Chapter 5): what pushes, what pulls, and why things stop
Every motion around you - a ball speeding up, a door swinging shut, a book staying put - is a story of forces. This chapter sorts them: forces that need touch and forces that act from a distance, plus friction, the quiet force that decides when moving things stop. Below: the ideas in plain words, then original EZT practice with worked answers. (Note: this is original practice, not a textbook exercise key.)
10 original worked examples, 10 fresh self-check questions, with explained answers. These are not copied textbook exercises, an official chapter index or a full answer key. No affiliation with NCERT is claimed.
Official sources for topic and edition context, checked 17 October 2026:
1. Force: a push or a pull
A force is a push or a pull acting on an object. It can change how fast something moves, the direction it moves, or its shape - or stop it entirely. Force is measured in newtons (N).
2. Contact forces
Contact forces act only when two objects touch: muscular force (pushing a cart, pulling a rope) and friction (the grip between surfaces in contact).
3. Non-contact forces
Non-contact forces act from a distance: magnetic force, electrostatic force, and gravitational force (gravity).
4. Balanced and unbalanced forces
When forces on an object cancel out, they are balanced - the object's motion does not change. When they do not cancel, the net (unbalanced) force changes the motion: a resting object starts moving, or a moving one speeds up, slows down or turns.
5. Friction: friend and foe
Friction opposes sliding between surfaces. It wears out shoe soles and machine parts, but without it we could not walk, write with a pencil, or stop a bicycle. Smoothing (polishing, oiling) reduces friction; treading and rough surfaces increase it.
Choose, solve, check, then try a fresh question.
Before calculating, read the method prompt and name the condition that makes it useful. Write your own attempt. Open the steps only when you need them, and use the check to catch a wrong sign, unit or interpretation. Finish with the fresh question before reading its answer.
Name the effect of a force
Choose the method: Ask whether the push or pull starts motion, stops motion, changes speed or direction, or changes shape.
EZT practice question
Name the effect of the force in each case: (a) kicking a resting football, (b) catching a thrown ball, (c) pressing a ball of dough flat.
Show the worked solution
- A kick makes the resting ball move.
- A catch brings the moving ball to rest.
- Pressing changes the dough from round to flat.
Answer: (a) starts motion; (b) stops motion; (c) changes shape.
Check: Each effect follows from a push or pull acting on the object.
Watch for this: A force need not always make something move; it can also stop or reshape it.
Now try it yourself
What effect does a push have on a stationary swing?
Check your answer
It starts the swing moving.
The applied push changes the swing from rest to motion.
Identify friction as a contact force
Choose the method: Look for two surfaces touching and opposing relative motion.
EZT practice question
A cycle slows down after you stop pedalling, even on a flat road. Which force is responsible, and is it contact or non-contact?
Show the worked solution
- The tyres and road touch.
- Friction between those surfaces opposes the motion, with a little help from air resistance.
Answer: Friction, a contact force.
Check: No magnet, charge or gravity is needed to explain the slowing on a flat road.
Watch for this: Gravity acts downward, but it is not the force directly opposing forward sliding here.
Now try it yourself
A book slides across a table and stops. Which force stops it?
Check your answer
Friction.
The touching table surface opposes the sliding motion.
Explain reduced grip
Choose the method: Smoother or lubricated contact usually reduces friction between two surfaces.
EZT practice question
Why is it easier to slip on a wet floor?
Show the worked solution
- Water sits between the shoe and floor.
- The water layer reduces the grip between the two surfaces.
Answer: The wet surface has less friction, so sliding is easier.
Check: A dry, rough sole usually gives better grip than a wet, smooth surface.
Watch for this: The floor is not pushing you; reduced friction lets your foot slide.
Now try it yourself
Why do rubber soles help on a wet path?
Check your answer
They increase friction and grip.
The sole material and tread make sliding less likely.
Recognise magnetic force
Choose the method: A magnetic force can act between a magnet and a magnetic material without contact.
EZT practice question
A magnet pulls an iron nail from across a table without touching it. Name the force type.
Show the worked solution
- The magnet and nail do not touch.
- The attraction is magnetic.
Answer: Magnetic force, a non-contact force.
Check: The nail moves before contact, so the force acts across a distance.
Watch for this: Do not call it friction; the surfaces are not touching when the pull begins.
Now try it yourself
A magnet moves a compass needle without touching it. Which force is acting?
Check your answer
Magnetic force.
Magnetic effects can act across a small distance.
Recognise electrostatic force
Choose the method: Rubbing can transfer charge, and a charged object can attract very light objects without contact.
EZT practice question
A balloon rubbed on dry hair picks up small paper bits. Which force is at work?
Show the worked solution
- Rubbing gives the balloon an electric charge.
- The charged balloon attracts the light paper pieces.
Answer: Electrostatic force.
Check: The paper moves before it touches the balloon, so this is non-contact.
Watch for this: The balloon is not acting as a magnet; the attraction comes from charge.
Now try it yourself
A comb rubbed on dry hair attracts tiny paper pieces. Name the force.
Check your answer
Electrostatic force.
The comb becomes charged and attracts light objects.
Name gravity and its direction
Choose the method: Gravity is the non-contact force that pulls objects towards the centre of the Earth.
EZT practice question
A thrown stone always falls back to the ground. Which force brings it down, and in which direction?
Show the worked solution
- After leaving the hand, the stone is pulled by gravity.
- The pull is towards the centre of the Earth.
Answer: Gravitational force, downwards.
Check: The stone returns even though nothing touches it while it is in the air.
Watch for this: Gravity does not push from above; it pulls towards the Earth.
Now try it yourself
A ball thrown straight up comes back down. Which force acts on it while it is in the air?
Check your answer
Gravity.
The Earth pulls the ball downward even after it leaves the hand.
Judge balanced forces
Choose the method: Equal forces in opposite directions cancel, so the net force is zero and motion does not change.
EZT practice question
In a tug of war, team A pulls with 300 N and team B with 300 N in the opposite direction. What happens to the rope?
Show the worked solution
- 300 N and 300 N act in opposite directions.
- Net force = 300 N - 300 N = 0 N.
Answer: The forces are balanced, so the rope does not accelerate.
Check: The rope may be stretched, but its position does not steadily move to either side.
Watch for this: Balanced does not mean no forces; it means the forces cancel.
Now try it yourself
Two students push a table from opposite sides with 150 N each. What is the net force?
Check your answer
0 N.
The equal opposite forces cancel.
Find the net force
Choose the method: For opposite forces, subtract the smaller magnitude; the larger side gives the direction.
EZT practice question
The same two teams tug, but team A now pulls with 320 N while team B pulls with 300 N. What changes?
Show the worked solution
- Net force = 320 N - 300 N = 20 N.
- The net force points towards team A.
Answer: A 20 N net force towards team A makes the rope accelerate that way.
Check: The forces no longer cancel, so motion changes.
Watch for this: Do not add opposite forces; subtract their magnitudes.
Now try it yourself
One person pushes a box with 100 N and another pushes opposite with 80 N. Find the net force.
Check your answer
20 N towards the 100 N push.
100 N - 80 N = 20 N in the stronger direction.
Explain why friction is useful
Choose the method: Walking needs grip between the shoe and ground; friction prevents the foot from slipping backwards.
EZT practice question
Give one reason friction is useful while walking.
Show the worked solution
- Your foot pushes backwards on the ground.
- Friction provides grip so the ground can push you forward.
Answer: Friction gives the grip needed to walk without slipping.
Check: It is harder to walk on ice because friction there is much lower.
Watch for this: Friction is not only a wasteful force; some motion depends on it.
Now try it yourself
Why is it difficult to walk on a polished icy surface?
Check your answer
There is too little friction.
The shoe cannot grip the surface well enough.
Increase friction where grip is needed
Choose the method: Rough surfaces and tread patterns increase friction between two contact surfaces.
EZT practice question
Why do bicycle tyres have treads?
Show the worked solution
- The tread pattern increases grip with the road.
- More grip helps the bicycle start, turn and brake safely.
Answer: Treads increase friction with the road for better grip.
Check: A completely smooth tyre has less grip, especially on rough or wet roads.
Watch for this: Do not confuse the chain, where oil reduces unwanted friction, with the tyre, where grip is useful.
Now try it yourself
Why do sports shoes often have patterned soles?
Check your answer
To increase friction and grip.
The sole pattern helps prevent slipping.
Try it yourself
Work these on paper before checking any notes. Answers are deliberately not shown here.
- Sort into contact and non-contact: friction, gravity, muscular force, magnetic force, electrostatic force.
- What force slows a sliding book on a table?
- Two boys push a box from opposite sides with equal force. Describe the motion.
- Name two effects a single force can produce at once when you squeeze and roll a ball of clay.
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Questions about this practice page
- What is a force?
- A push or a pull on an object, measured in newtons, that can change its speed, direction or shape.
- What is the difference between contact and non-contact forces?
- Contact forces (muscular force, friction) need the objects to touch; non-contact forces (magnetic, electrostatic, gravitational) act across a distance.
- What is friction?
- The contact force that opposes sliding between two surfaces - it is why moving things slow down and also why we can walk without slipping.
- What happens when forces on an object are balanced?
- They cancel out, so the object's motion does not change - it stays at rest or keeps moving at the same speed and direction.
- Are these the NCERT Exploring Forces exercise questions?
- No. EZT pages are original practice on this chapter - use them to prepare for the textbook exercises, not as a substitute for your book.