A batsman hits a cricket ball, which then rolls on a level ground. After covering a short distance, the ball comes to rest. The ball slows down to stop because:
The cricket ball comes to rest after covering a short distance, because there is a force on the ball, opposing the motion. This force is due to resistance of air and also due to friction between the ball and the ground.
The force of freely falling body is directly proportional to:
The acceleration of an object is directly proportional to the net force acting on the object and inversely proportional to the object's mass.
The principle of conservation of linear momentum states that in a system it :
Law of Conservation of Momentum
In general, the law of conservation of momentum or principle of momentum conservation states that the momentum of an isolated system is a constant. The vector sum of the momenta (momentum is equal to the mass of an object multiplied by its velocity) of all the objects of a system cannot be changed by interactions within the system. In classical mechanics, this law is implied by Newton’s laws. This principle is a direct consequence of Newton’s third law.
A porter is carrying a weight of 200 N on his head. If the force exerted on his head is taken as action, then the reaction force is exerted by :
Which of the following are vector quantities:
Two bodies collide at the same time. Which of the following is conserved?
In a inelastic collision only momentum is conserved. Kinetic energy is not conserved Loss of heat may takes place so temperature is not conserved. Since Kinetic energy is not conserved, velocity is not conserved.
Impulse is equal to :
In a collision, an object experiences a force for a specific amount of time that results in a change in momentum. The result of the force acting for the given amount of time is that the object's mass either speeds up or slows down (or changes direction). The impulse experienced by the object equals the change in momentum of the object. In equation form, F • t = m • Δ v.
A rocket works on the principle of:
Rocket works on the conservation of momentum. In a rocket, the fuel burns and produces gas at high temperature. These gases are ejected out of the rocket from a nozzle at the back side of the rocket. The ejecting gas exerts a forward force on the rocket which help in accelerating. Through the mass of gases escaping per second is very small and their momentum is very large due to their tremendous velocity of escape. An equal and opposite momentum is imparted to the rocket which despite its large mass builds up a high velocity.
When a speeding car takes a sharp turn, the persons sitting in it experience outward pull. This happens due to:
The ratio of force and acceleration of a moving body is the measure of its:
When you kick a stone, you get hurt. Due to which property this happens?
This happens due to Newton's third law of motion.'To every action, there is always an equal and opposite reaction.'When you kick a stone, you apply some force on it. To maintain the Law of Conservation of momentum, the stone also exerts a force on the leg, which we feel as pain.
A car accelerates on a horizontal road due to the force exerted by
The car pushes the ground in the backward direction and according to the third law of motion, reaction force of the ground in the forward direction acts on the car.
Impulse has same unit as that of:
By Newton's second law, the physical quantity which can be calculated, if we know the magnitude of force on a given mass is :
A body is moving with a constant momentum. The motion of the body is :
It will have a constant momentum, change in momentum would be zero. It has exception of non-inertial frame of reference, wherein the change in mass occurs at higher speeds. If the body moves with speed of light, it will have no mass and hence no momentum. It will have linear momentum since its velocity is not zero.
A cracker at rest explodes into two equal parts. These parts will move in :
In order to conserve momentum the two parts move in the opposite direction and have same momentum.
A batsman has a choice to use heavy or light bat, while facing a fast bowler. He will prefer:
Heavier the bat, less will be velocity of recoil for the change in momentum and hence less strain on the hands.
A vehicle has a mass of 1500 kg. If the vehicle is to be stopped with a negative acceleration of 1.7 ms–2, the force of friction between the vehicle and road is :
Mass of the vehicle, m = 1500 kg
Acceleration, a = – 1.7 m s–2
Force acting between the vehicle and road, F =?
We know that, F = m x a
Therefore, F = 1500 kg X 1.7 m s–2
Or, F = – 2550 N
Thus, force between vehicle and road = - 2550 N. Negative sign shows that force is acting in the opposite direction of the vehicle.
A man while running at a constant acceleration of 3.5 ms–2, develops a force of 280 N. The mass of man is:
The mass of an aeroplane is 2.5 t. Its engine develops a force of 8750 N before taking off. The acceleration of the aeroplane at the time of take off is :
A horse while running at a constant velocity of 15 ms–1, develops a momentum of 3000 Ns. The mass of horse is:
Momentum = mass × velocity
mass = momentum/velocity
= 3000/15 =200 kg
A truck starts from rest and rolls down the hill with a constant acceleration. It travels 400 m in 20 s. If the mass of truck is 7 metric tonnes, the force acting on it is:
The truck starts from rest, so initial velocity = 0
Distance travelled = 400 m
Time taken = 20 s
We know the equation of motion, S = ut + ½ at2
400 = 0 + ½ a * (20)2
a = 2 m/s2
Now, mass = 7 metric tonnes
= 7 * 1000
= 7000 kg
So force = mass * acceleration
F = 7000 * 2
= 14000 N
A bullet of mass 0.01 kg is fired from a rifle. The bullet takes 0.003 s to move through the barrel and leaves with a velocity of 300 ms–1. The acceleration acting on the bullet is :
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 40,000 N and track offers a friction of 5000 N, then net accelerating force acting on the system is:
Given, force of engine = 40000 N
Force of friction = 5000 N
Mass of engine = 8000 kg
Total weight of wagons = 5 x 2000 kg = 10000 kg
(a) The net accelerating force
= Force exerted by engine – Force of fricition
= 40000 N – 5000 N = 35000 N