tion:Newton’s LawsIn 1687, Isaac Newton created three laws of motion to describe the relationship between a body and the forces acting upon it, and how the body moves in response to those forces.Part ofPhysics (Single Science)Forces, space and radioactivityAdd to My BitesizeShareReviseTestSign in, save timeWe’ll remember what you’ve looked at so you can jump back in.Sign in or Register to personalise your Bitesize now.1234567Newton’s Second LawUnbalanced forcesWhen the forces acting on an object do not balance, the resultant force will cause the object to accelerate in the direction of the resultant force.In other WORDS, a resultant force on a body will cause it to change its velocity. This simply means that UNBALANCED forces will cause:accelerationdecelerationchange in directionA resultant force is the leftover or net force when all the forces acting on the object have been combined.The relationship between the resultant force, the mass of the object and the object’s acceleration is:You will have to be able to state this equation in the examination.QuestionA car weighs 1,000 kg. The resultant force is 5,000 N. Use the Fma triangle to find the acceleration of the car.Reveal answerResultant force and calculating accelerationTo calculate the acceleration, you must find the resultant force so that you can divide it with the car's mass.The resultant force = 4,000 N - 1,000 N = 3,000 N= 3,000 N ÷ 1,000 kg= 3 m/s2The first car accelerates because the car is moving in the same direction as the resultant force. Now look at the second car.Resultant force = -7,000 N= -7,000 N ÷ 1,000 kg= -7 m/s2The second car decelerates. It is moving in the opposite direction to the resultant force.Acceleration and mass are inversely proportional. This means that if the mass of the vehicle doubles, the acceleration halves if the resultant force doesn’t change.Resultant force and acceleration are directly proportional. If the resultant force doubles, the acceleration of the vehicle also doubles if the mass of the vehicle is the same.QuestionA car has a mass of 1,200 kg, and an engine that can DELIVER a force of 6,000 N. Find the acceleration of the car.Reveal answerQuestionFind the force developed by a speed BOAT engine, if the boat has a mass of 300 kg and can accelerate at a rate of 1.5 m/s2.Reveal answerQuestionIn a theme park, one of the rides has a motor that can deliver a force of 3,600 N to an empty passenger car, causing it to accelerate at 4.5 m/s2.Find the mass of the car.Reveal answer1234567GlossaryMore GuidesDistance, speed and acceleration – WJECNewton’s Laws – WJECWork and energy – WJECFurther motion concepts – WJECStars and planets – WJECThe Universe – WJECTypes of radiation – WJECHalf-life – WJECNuclear decay and nuclear energy – WJECStruggling to get your head round revision and exams?Our team of exam survivors will get you started and KEEP you going.