Its velocity is slowed down to 18 km/h in 4 s by an unbalanced external force. Therefore, her initial momentum = 64 × 12Ī motor car of mass 1100 kg is moving along a straight line with a uniform velocity of 90 km/h. What are her momenta in each case? Solution: When she gets closer to the finish line, she slows down to 8 m/s. Example 1:Īn athlete weighing 64 kg runs a race at a speed of 12 m/s. Thus, a body at rest has no momentum at all. Mathematically, if a body is at rest, then its speed is zero. Thus, momentum being the amount of motion contained in a body, is also zero. For example, a tree is always at rest, i.e., it has no motion.
The momentum of a body at rest:Ī body at rest has no motion at all. The momentum of an object is directed along with its velocity. Momentum is a vector quantity, like velocity, in its formula, is a vector quantity.
Thus, the SI unit of momentum is “ kg.m/s“. Therefore, the SI unit of p = SI unit of mass x SI unit of velocity. The SI unit of mass is ‘ kg’ and of velocity is ‘ m/s.’ The SI unit of momentum can be derived by plugging the SI units of mass and speed in the formula above. Therefore, the momentum can be mathematically written as, Now, it can be concluded that the momentum is directly proportional to the moving object’s mass and speed or velocity. When this stone hits the glass door, it breaks it. The speed of the marble can be increased by throwing it using a slingshot, as shown in figure 7.2, thus, increasing its speed. One way to increase the momentum of the marble is to increase its speed. However, it can also break the toughened glass if its momentum is somehow increased. The marble has a small mass, unlike the stone. It means that the momentum of an object increases when its speed increases.įurther, it is possible to use the smaller marble and get the same impact, which can be caused by the larger stone breaking the toughened glass door. Therefore, it can be concluded that the momentum of an object increases with increasing speed, i.e., momentum varies directly as the speed. Thus, the ball thrown by the father has greater momentum than the same ball thrown by the child. When thrown by the child, the ball moves with a much lesser speed than the speed it acquires when thrown by his father. This difference in the impact (the distance moved by the ball) in each case is different because of the difference in velocity acquired by the ball. Suppose a ball is thrown by a child and his father, The ball thrown by the father would move to a greater distance because he is stronger than his child. It shows the fastness of motion of an object or the strength of the impact that the moving object would cause. It is defined as the amount of motion contained in an object. The greater the force imparted, the greater the momentum imparted, the faster the object moves. Such activities are said to provide momentum to the ball. In all these cases, a force is applied to a ball, and that makes it move faster. The balls would rather move slowly if these activities are not done. All these activities are performed to make the ball move with great speed when hit/thrown. The velocity of a body of mass 10 kg increases from 4 m/s to 8 m/s when a force acts on it for 2 s.In our daily life, we make many observations, such as a fast bowler taking a run-up before bowling, a tennis player moving her racket backward before hitting the tennis ball and a batsman moving his bat backward before hitting the cricket ball.What is the momentum before the force acts? The velocity of a body of mass 10 kg increases from 4 m/s to 8 m/s when a force acts on it for 2s.On what factors does the momentum of a body depend ?(b) Calculate the change in momentum of a body weighing 5 kg when its velocity decreases from 20 m/s to 0.20 m/s. Question 36:(a) Define momentum of a body.A body is moving with uniform acceleration.What do we get by the product of mass and velocity?I.What will be the momentum of a body of mass ‘m’ which is moving with a velocity 'v' ?.The body is having mass $4\ kg$ and moving with initial velocity $20\ m/s$, find out its momentum.The rockets work on the principle of conservation of:(a) mass(b) energy(c) momentum(d) velocity.Rocket works on the principle of conservation of$(a)$.The velocity of a body of mass $10\ kg$ increases from $4\ m/s$ to $8\ m/s$ when a force acts on it for $2\ s$.(a) What is the momentum before the force acts?(b) What is the momentum after the force acts? (c) What is the gain in momentum per second?(d) What is the value of the force?.
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