Question:
Why does a bicycle slow down when the cyclist stop pedalling?
Answer:
This is because of the frictional forces acting opposite to the direction of motion.
Force and Laws of Motion
Q 1.
Using second law of motion, derive the relation between force and acceleration.
Q 2.
Do action-reaction forces produce the same magnitude of acceleration ?
Q 3.
What is the total momentum of a bullet and a gun before firing?
Q 4.
Are action-reaction forces simultaneous ?
Q 5.
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 6.
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 7.
Can balanced forces move a body at rest ?
Q 8.
Define momentum of a body.
Q 9.
Can balanced forces change the shape and size of an object?
Q 10.
On what factor does inertia of a body depend ?
Q 11.
It is difficult to balance our body when we accidentally slip on a peel of banana. Explain why?
Q 12.
What is collision? What are the types of collision?
Q 13.
Fill in the blanks :
The study of motion of a body under the action of a force is called ______.
Q 14.
Which law of motion gives the measure of force?
Q 15.
Which Newton's law is also known as the Law of Inertia?
Q 16.
Define inertia. How it is measured?
Q 17.
Name the principle on which a rocket works.
Q 18.
How is force related to acceleration produced in a body by its application?
Q 19.
What is the SI unit of impulse.
Q 20.
Name the physical quantity that corresponds to the rate of change of momentum.
Q 21.
What is the momentum of a man of mass 75 kg when he walks with a velocity of 2 m/s ?
Q 22.
For how long should a force of 100 N act on a body of mass 20 kg so that it acquires a velocity of 100 m/s ?
Q 23.
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 24.
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
?
Q 25.
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 26.
When a branch of a tree is shaken, some of the fruits may fall down.Why ?
Q 27.
A person in a bus tends to fall backwards, when it starts suddenly ?
Q 28.
Explain why a player lowers his hands while catching a cricket ball.
Q 29.
Justify Newton's first law gives notion (or definition) about force.
Q 30.
Explain why some of the leaves may get detached from a tree if we vigorously shake its branch.
Q 31.
Define 1N (Newton).
Q 32.
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 33.
How Newton's Second law of motion is different from First law?
Q 34.
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 35.
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 36.
While catching a fast moving ball, fielder gradually pulls his hand backwards. Give reasons.
Q 37.
When two objects act on each other, does action-reaction force pair cancel out each other?
Q 38.
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 39.
Using a horizontal force of 200 N, we intend to move a wooden cabinet across a floor at a constant velocity. What is the friction force that will be exerted on the cabinet?
Q 40.
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 41.
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 42.
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 43.
Fill in the blanks :
The natural tendency of objects to resist a change in their state of rest or of uniform motion is called ______.
Q 44.
Fill in the blanks :
An umbrella protects us from rain it is based on the property of _____________.
Q 45.
Fill in the blanks :
When a car enters a curved path, the person sitting in it is thrown outwards. This is because of the property of ______________.
Q 46.
Fill in the blanks :
Which has more inertia of Cricket ball or a rubber ball of the same size? __________
Q 47.
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 48.
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 49.
Fill in the blanks :
________ is a measure of intertia.
Q 50.
Fill in the blanks :
When a hanging carpet is beaten with stick, the dust particles start coming out of it. It is due to ______________.
