12/10/2023 0 Comments Newtons 2nd law of motionIn one experiment, we will be changing the mass of the object, whilst in the other we will change the force applied to the object. We can investigate the acceleration of an object using the following method. Now we can use the formula F = ma to find the force on the cyclist (plus his bike). We can estimate the mass of the cyclist with his bike may be around 90kg.ĥ. Using the speed and time, we can work out the acceleration of the cyclist.Īcceleration = change in velocity / time takenĤ. As an estimate, we could say that it takes about 12 seconds to reach this speed.ģ. We can estimate the time taken to reach this speed. From our table, we know that the average speed of a train is about 6m/s.Ģ. Question: Estimate the force experienced by a cyclist and his bike when he accelerates from rest to a typical speed.ġ. It indicates to the examiner that the value you are giving is an approximate answer only. You should be able to use the symbol ‘ – ’ when talking about ̴ approximations. Some exam questions my ask you to estimate the accelerations and forces involved with different forms of transport. You can find some average speeds in the table we outlined in the section on acceleration. Previously, we discussed some common forms of transport, such as cycling, walking and driving a car. The higher the inertial mass, the more difficult it is to change the velocity of the object. We can use the inertial mass to determine how ‘difficult’ it is to change the velocity of an object. Inertial mass is the ratio of force over acceleration. This means that inertial mass can be defined as follows: Since Newton’s Second Law is F = ma, we can rearrange this to give us m = F / a. We can use Newton’s Second Law to help us find a value for inertial mass. Question: Calculate the mass of a spaceman who accelerates at 1.5m/s² when pushed with a force of 150N.įor this question, we want to rearrange the equation to find mass. acceleration, a, in metres per second squared, m/s².We can calculate resultant force using the following formula. We also know that the acceleration is inversely proportional to the mass of the object (as the mass increases, the acceleration decreases).Ĭalculating Resultant Force Formula for Resultant Force We know that the acceleration of an object is proportional to the force acting on it (as the force increases, the acceleration increases). In Newton’s Second Law, there are relationships of proportionality. The car is much lighter than the truck, so will experience a larger acceleration. Mass – the heavier an object is, the more force needed to accelerate it, and hence the lower the acceleration for a given resultant force.įor example, both vehicles below have a resultant force of 2N.Remember, if the resultant force is zero, the object is at constant speed and does not accelerate. Resultant Force – The larger the resultant force, the larger the acceleration.The size of the acceleration (positive or negative) depends on two factors: Newton’s Second Law helps us understand how we can measure the size of this acceleration or deceleration. In the previous tutorial we learnt that a resultant force means that an object is accelerating or decelerating. Newton's Second Law (GCSE Physics) Newton’s Second Law Newton’s Second Law
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