Physics

Force and Laws of Motion

Question:

How Newton's Second law of motion is different from First law?

Answer:

Newton’s first law of motion deals with the behaviour of objects on which all existing forces are balanced. It gives us notion of external force required to change the inertia state of the object.

While the second law of motion deals with the behaviour of objects on which all existing forces are not balanced. It gives us a measure of the force.

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Force and Laws of Motion

Q 1.

Derive the unit of force using the second law of motion. A force of 5 N produces an acceleration of 8 m s-2 on a massm1 and an acceleration of 24m s-2 on a mass m2.What acceleration would the same force provide if both the masses are tied together ?

Q 2.

When a carpet is beaten with a stick, dust comes out of it. Explain.

Q 3.

Define intertia.

Q 4.

State Newton’s three laws of motion.

Q 5.

Why do we tend to fall outwards when a car takes a steep turn?

Q 6.

What would be the force required to produce an acceleration of 2 m/s2 in a body of mass 12 kg ? What would be the acceleration if the force were doubled ?

Q 7.

A stone of 1 kg is thrown with a velocity if 20 ms-1 across the frozen surface of a lake and comes to rest after travelling a distance of 50 m.What is the force of friction between the stone and the ice ?

Q 8.

Why is it advised to tie any luggage kept on the roof of a bus with a rope?

Q 9.

Two persons manage to push a motorcar of mass 1200 kg at a uniform velocity along a level road. The same motorcar can be pushed by three persons to produce an acceleration of 0.2m s-2. With what force does each person push the motorcar?
(Assume that all persons push the motorcar with the same muscular effort.)
 

Q 10.

When a force acts on a body, what are the two essential effects it can produce?

Q 11.

Define force.

Q 12.

What is one newton force ?

Q 13.

Derive the relation F = ma,where the symbols have their usual meanings.

Q 14.

Justify Newton's first law gives notion (or definition) about force.

Q 15.

While catching a fast moving ball, fielder gradually pulls his hand backwards. Give reasons.

Q 16.

State Law of conservation of momentum.

Q 17.

Fill in the blanks :
When a hanging carpet is beaten with stick, the dust particles start coming out of it. It is due to ______________.

Q 18.

Force can change the shape and size of an object. Give an example.

Q 19.

What are unbalanced forces?

Q 20.

What do you mean by an imapct force?

Q 21.

A force of 5 N gives a mass m1 an acceleration of 10 m/s2,and a mass m2,an acceleration of 20 m/s2.What acceleration would it give if both the masses were tied together ?

Q 22.

Two objects of masses 100 g and 200 g are moving along the same line in the same direction with velocities of 2 m/s and 1 m/s,respectively.They collide and after the collision, the first object moves at a velocity of 1.67 m/s in the same direction.Determine the velocity of the second object

Q 23.

A hockey ball of mass 200 g travelling at 10 m/s is struck by a hockey stick so as to return it along its original path with a velocity of 5 m/s.Calculate the change in momentum of the hockey ball by the force applied by the hockey stick.

Q 24.

What is the SI unit of force ?

Q 25.

Is momentum a scalar or vector ?

Q 26.

Define momentum of a body.

Q 27.

An unloaded truck weighing 2000 kg has a maximum acceleration of 0.4 m/s2.What is the maximum acceleration, when it carries a load of 2000 kg ?

Q 28.

Explain what is meant by momentum of a body.Is it a scalar or a vector ? What are its units ?

Q 29.

Establish relation between inertia and mass.

Q 30.

Why does a gun recoil on firing ? Obtain an expression for recoil velocity of gun.

Q 31.

State Newton’s first law of motion. Hence define force and inertia.

Q 32.

State Newton’s second law of motion and establish that F = ma where symbols have their usual meanings.

Q 33.

Give atleast four applications of Newton’s second law of motion.

Q 34.

State and explain Newton’s third law of motion.How will you prove it experimentally ?

Q 35.

Explain briefly any three applications of Newton’s third law of motion.

Q 36.

Which of the following has more inertia:
(a) a rubber ball and a stone of the same size?
(b) A bicycle and a train?
(c) A five-rupee coin and a one-rupee coin?

Q 37.

State Newton's First Law of motion.

Q 38.

Explain why some of the leaves may get detached from a tree if we vigorously shake its branch.

Q 39.

Why do you fall in the forward direction when a moving bus brakes to a stop and fall backwards when it accelerates from rest?

Q 40.

Define momentum.

Q 41.

What are balanced and unbalanced forces?

Q 42.

If the set of forces acting on an object are balanced, then object

(a) must be at rest.
(b) must be moving
(c) must not be accelerating.
(d) none of these.

Q 43.

An object experiences a net zero external unbalanced force. Is it possible for the object to be travelling with a non-zero velocity? If yes, state the conditions that must be placed on the magnitude and direction of the velocity. If no, provide a reason.

Q 44.

Which of the following graph represents unbalanced force.

Q 45.

Define 1N (Newton).

Q 46.

What is the unit of force in c.g.s system?

Q 47.

A truck starts from rest and rolls down a hill with a constant acceleration. It travels a distance of 400 m in 20 s. Find its acceleration. Find the force acting on it if its mass is 7 metric tonnes. (Hint: 1 metric tonne = 1000 kg.)

Q 48.

A stone of 1 kg is thrown with a velocity of 20 m s-1 across the frozen surface of a lake and comes to rest after travelling a distance of 50 m. What is the force of friction between the stone and the ice? (Calculate time taken and acceleration also).

Q 49.

An automobile vehicle has a mass of 1500 kg. What must be the force between the vehicle and road if the vehicle is to be stopped with a negative acceleration of 1.7 ms-2.
 

Q 50.

According to the third law of motion when we push on an object, the object pushes back on us with an equal and opposite force. If the object is a massive truck parked along the road side, it will probably not move. A student justifies this by answering that the two opposite and equal forces cancel each other. Comment on this logic and explain why the truck does not move.