Question:
Explain why some of the leaves may get detached from a tree if we vigorously shake its branch.
Answer:
Some leaves of a tree get detached when we shake its branches vigorously is due to inertia of rest. When the tree moves to and fro, leaves tend to remain in the rest state and resist the change. Due to this, some leaves gets detached and fall down.
Force and Laws of Motion
Q 1.
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 2.
Do action-reaction forces produce the same magnitude of acceleration ?
Q 3.
On what factor does inertia of a body depend ?
Q 4.
Are action-reaction forces simultaneous ?
Q 5.
What is the unit of force in c.g.s system?
Q 6.
Using second law of motion, derive the relation between force and acceleration.
Q 7.
In the above question, which body is damaged more ?
Q 8.
Fill in the blanks :
The study of motion of a body under the action of a force is called ______.
Q 9.
Can balanced forces change the shape and size of an object?
Q 10.
Can every force produce motion in every object?
Q 11.
Explain why a player lowers his hands while catching a cricket ball.
Q 12.
When a branch of a tree is shaken, some of the fruits may fall down.Why ?
Q 13.
A car weighs 1500 kg.Its speed time graph is shown in Fig. Calculate the force required at the end of 5 seconds to bring the car to a stop within one second.
Q 14.
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 15.
What acceleration is produced by a force of 5 N acting on a body of mass 20 kg ?
Q 16.
A TV set is lying on a table. The TV set experiences a gravitational force (pull) downwards (FW) by the Earth. It also experiences a force on it due to table in contact i.e. (FTable-TV) in upward direction. Do these forces form an action-reaction pair? Do these forces follow Newton's third Law of motion?
Q 17.
Can balanced forces change the shape and size of a body ?
Q 18.
The masses of two objects are 2 kg and 20 kg. Which has greater inertia ?
Q 19.
It is difficult to balance our body when we accidentally slip on a peel of banana. Explain why?
Q 20.
What is the total momentum of a bullet and a gun before firing?
Q 21.
A stone of 1 kg is thrown with a velocity if 20
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 22.
Define momentum of a body.
Q 23.
State why Newton's first law of motion is called law of inertia.
Q 24.
A body of mass 25 kg has momentum of 125 kg m/s. What is the velocity of the body?
Q 25.
Why is it easier to stop a tennis ball in comparison to a cricket ball moving with the same speed ?
Q 26.
State Law of conservation of momentum.
Q 27.
Fill in the blanks :
When the playing card is flicked with the finger the coin placed over it falls in the tumbler. It is due to ____________.
Q 28.
Define force of friction.
Q 29.
What is the SI unit of impulse.
Q 30.
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 31.
A bullet of mass 10 g travelling horizontally with a velocity of 150
strikes a block and comes to rest in 0.03 s. Calculate the distance of penetration of the bullet into the block.Also, calculate the magnitude of the force exerted by the wooden block on the bullet.
Q 32.
What is the SI unit of momentum ?
Q 33.
Explain the use of seat belts in cars.
Q 34.
In the following example, try to identify the number of times the velocity of the ball changes:
A football player kicks a football to another player of his team who kicks the football towards the goal. The goalkeeper of the opposite team collects the football and kicks it towards a player of his own team?
Also identify the agent supplying the force in each case.
Q 36.
When a carpet is beaten with a stick, dust comes out of it. Explain.
Q 37.
Why is it advised to tie any luggage kept on the roof of a bus with a rope?
Q 38.
Which of the following graph represents unbalanced force.
Q 39.
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 40.
The speed-time graph of a car is shown below. The car weighs 1000kg.
(i) Find the distance covered by the in fits two seconds.
(ii) Find how much force is applied by the car brakes in the fifth second so that the car comes to an halt by sixth second.
Q 41.
Is force a scalar or vector quantity?
Q 42.
Which principle is involved in the working of a jet plane?
Q 43.
A constant force acts on an object of mass 5 kg for a duration of 2 s.It increases the object’s velocity from 3 m/s to 7 m/s.Find the magnitude of the applied force. Now if the force were applied for a duration of 5 s,what would be the final velocity of the object ?
Q 44.
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 45.
What is force ? What is inertia ? How is inertia measured ?
Q 46.
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 47.
Explain, why is it difficult for a fireman to hold a hose, which ejects large amounts of water at a high velocity.
Q 48.
Law of conservation of momentum is applicable to an isolated system. What do you mean by an isolated system?
Q 49.
A motorcar of mass 1200 kg is moving along a straight line with a uniform velocity of 90 km/h. Its velocity is slowed down to 18 km/h in 4 s by an unbalanced external force. Calculate the acceleration and change in momentum. Also calculate the magnitude of the force required.
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.
