assertion: change in momentum impulse. reason: impulse is the area between (F-t) graph and x axis
Answers
Explanation:
In a previous part of Lesson 1, it was said that
In a collision, an object experiences a force for a given amount of time that results in its mass undergoing a change in velocity (i.e., that results in a momentum change).
There are four physical quantities mentioned in the above statement - force, time, mass, and velocity change. The force multiplied by the time is known as the impulse and the mass multiplied by the velocity change is known as the change in momentum. The impulse experienced by an object is always equal to the change in its momentum. In terms of equations, this was expressed as
This is known as the impulse-momentum change theorem.
In this part of Lesson 1, we will examine some real-world applications of the impulse-momentum change theorem. We will examine some physics in action in the real world. In particular, we will focus upon
the effect of collision time upon the amount of force an object experiences, and
the effect of rebounding upon the velocity change and hence the amount of force an object experiences.
As an effort is made to apply the impulse-momentum change theorem to a variety of real-world situations, keep in mind that the goal is to use the equation as a guide to thinking about how an alteration in the value of one variable might affect the value of another variable.
The Effect of Collision Time Upon the Force
First we will examine the importance of the collision time in affecting the amount of force that an object experiences during a collision. In a previous part of Lesson 1, it was mentioned that force and time are inversely proportional. An object with 100 units of momentum must experience 100 units of impulse in order to be brought to a stop. Any combination of force and time could be used to produce the 100 units of impulse necessary to stop an object with 100 units of momentum. This is depicted in the table below.
Combinations of Force and Time Required to Produce 100 units of Impulse
Force
Time
Impulse
100
1
100
50
2
100
25
4
100
10
10
100
4
25
100
2
50
100
1
100
100
0.1
1000
100
Observe that the greater the time over which the collision occurs, the smaller the force acting upon the object. Thus, to minimize the effect of the force on an object involved in a collision, the time must be increased. And to maximize the effect of the force on an object involved in a collision, the time must be decreased.
Both assertion and reason are true but reason is not the correct explaination of assertion.
- The impulse is a measurement of how much it modifies an object's momentum. It is taken as the product of force and time.
- The momentum of an object that is not moving is zero. A massive, slow-moving object has a lot of momentum. A small, fast-moving item has a lot of momentum.
- To determine the impulse from a graph we calculate the area that comes under the (F-t) graph.