Question:
Can balanced forces stop a moving body ?
Force and Laws of Motion
Q 1.
Are action-reaction forces simultaneous ?
Q 2.
Do action-reaction forces produce the same magnitude of acceleration ?
Q 3.
What is the unit of force in c.g.s system?
Q 4.
On what factor does inertia of a body depend ?
Q 5.
Explain why a player lowers his hands while catching a cricket ball.
Q 6.
Can every force produce motion in every object?
Q 7.
What is the SI unit of impulse.
Q 8.
The masses of two objects are 2 kg and 20 kg. Which has greater inertia ?
Q 9.
It is difficult to balance our body when we accidentally slip on a peel of banana. Explain why?
Q 10.
While driving on a highway, an insect strikes on the car windshield and splatters. Which experiences greater impact (force): an insect or the windshield?
Q 11.
Can balanced forces change the shape and size of an object?
Q 12.
A man pushes a box of mass 50 kg with a force of 80 N. What will be the acceleration of the box due to this force? What would be the acceleration if the mass were doubled ?
Q 13.
An object of mass 1 kg travelling in a straight line with a velocity of 10 m/s collides with, and sticks to, a stationary wooden block of mass 5 kg. Then they both move off together in the
same straight line. Calculate the total momentum just before the impact and just after the impact. Also, calculate the velocity of the combined object.
Q 14.
Fill in the blanks :
The study of motion of a body under the action of a force is called ______.
Q 15.
A certain force exerted for 1 -2 s raises the speed of an object from 1.8 m/s to 4.2 m/s. Later,the same force is applied for 2 second. How much does the speed change in 2 s ?
Q 16.
When a branch of a tree is shaken, some of the fruits may fall down.Why ?
Q 17.
Fill in the blanks :
When a bus starts suddenly, the bus passengers standing in the bus tend to fall backwards. It is due to _______________.
Q 18.
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 19.
A body of mass 25 kg has momentum of 125 kg m/s. What is the velocity of the body?
Q 20.
An object of mass 5 kg is moving with a velocity 4 m/s. A constant force of 20 N acts on the object. What will be the velocity after 3 s.
Q 21.
Fill in the blanks :
It is dangerous to jump out of a moving bus because due to _________ one falls forward.
Q 22.
Define 1 Newton force.
Q 23.
Derive the unit of force using the second law of motion. A force of 5 N produces an acceleration of
on a mass
and an acceleration of 24
on a mass
.What acceleration would the same force provide if both the masses are tied together ?
Q 24.
Discuss briefly Galileo's ideas about motion.
Q 25.
Define 1N (Newton).
Q 26.
Which law of motion gives the measure of force?
Q 27.
Name the physical quantity that corresponds to the rate of change of momentum.
Q 28.
Why is the person hurt less when he falls on a spongy surface?
Q 29.
A bullet of mass 20 gram moving with a velocity of 300 m/s gets embedded in a freely suspended wooden block of mass 880 gram.What is the velocity acquired by the block ?
Q 30.
Two hockey players of opposite teams,while trying to.hit a hockey ball on the ground collide and immediately become entangled.One has a mass of 60 kg,and was moving with a velocity 5.0 m/s,while the other has a mass of 55 kg and was moving faster with a velocity of 6.0 m/s towards the first player,In which direction and with what velocity will they move after they become entangled ? Assume that the frictional force acting between the feet of the two players and ground is negligible.
Q 31.
Name the unbalanced force that stops a ball rolling on the ground.
Q 32.
What is the other name for Newton's first law of motion ?
Q 33.
In the above question, which body is damaged more ?
Q 34.
A ball is thrown vertically upwards. What is its momentum at the highest point ?
Q 35.
Derive the relation F = ma,where the symbols have their usual meanings.
Q 36.
Why does a gun recoil on firing ? Obtain an expression for recoil velocity of gun.
Q 37.
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 38.
When a carpet is beaten with a stick, dust comes out of it. Explain.
Q 39.
What are contact forces? Give examples
Q 40.
What are non-contact forces? Give examples.
Q 41.
What's the relation between 1N and 1 dyne?
Q 42.
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 43.
A hammer of mass 500 g, moving at 50 m/s, strikes a nail. The nail stops the hammer in a very short time of 0.01 s. What is the force of the nail on the hammer ?
Q 44.
State Newton's third law of motion.
Q 45.
Explain, why is it difficult for a fireman to hold a hose, which ejects large amounts of water at a high velocity.
Q 46.
Suppose a ball of mass m is thrown vertically upward with an initial speed v, its speed decreases continuously till it becomes zero. Thereafter, the ball begins to fall downward and attains the speed v again before striking the ground. It implies that the magnitude of initial and final momentums of the ball are same. Yet, it is not an example of conservation of momentum. Explain why ?
Q 47.
From a rifle of mass 4 kg, a bullet of mass 50 g is fired with an initial velocity of 35 m/s. Calculate the initial recoil velocity of the rifle.
Q 48.
A hockey ball of mass 200 g travelling at 10 m s-1 is struck by a hockey stick so as to return it along its original path with a velocity at 5 m s-1. Calculate the change of momentum occurred in the motion of the hockey ball by the force applied by the hockey stick.
Q 49.
A 8000 kg engine pulls a train of 5 wagons, each of 2000 kg, along a horizontal track. If the engine exerts a force of 40000 N and the track offers a friction force of 5000 N, then calculate:
(a) the net accelerating force;
(b) the acceleration of the train; and
(c) the force of wagon 1 on wagon 2.
Q 50.
Two objects having their masses in ratio 3:5 are acted upon by two forces each on one object. The forces are in the ration of 5:3. Find the ratio in their accelerations.
