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# force and laws of motion test questions

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Newton's laws of motion

Newton's laws of motion consist of three physical law s that form the basis for classical mechanics. They describe the relationship between the forces acting on a body and its motion due to those forces. They have been expressed in several different ways over nearly three centuries, and can

Question:OK, this is really difficult, and I really need help on how to do it. Here's the question: A Particle of mass 6kg starts from rest and accelerates uniformly. The resultant force on the particle is 15N. Find the time taken to reach a speed of 10ms^-1

Answers:Acceleration , a = F / m = 15 / 6 = 2.5 m/s Speed after time t is : v = 10 = at t = 10 / 2.5 t = 4 s

Question:My teacher said to day that 'Second Law of Motion' i.e. F directly proportional to p/t (p=momentum) is the basic law of motion as both the 1st and 3rd laws are contained in it. I somehow figured out how 1st law can be derived from 2nd law, can someone tell me how 3rd law is contained in the second law ?? Any mathematically deduced or logical reasoning answer would be perfect! Please I need help ASAP! Thnx!!!!

Answers:Newton's 3rd law is that of conservation of momentum. If you look at two objects exerting forces on each other their equal and opposite forces with cancel each other out and you will be left with only the external forces on each object. But, since that momentum must remain constant than the derivative of that momentum (P') must be 0. (P')= ma because a=dv/dt and P=mv so P'=mv'

Question:This is so confusing I don't really like physics and this is one of the many questions I will be asking. I have a test coming up and these are review q's please explain the process. A race car has a mass of 706 kg. It starts from rest and travels 35.0 m in 3.0 s. The car is uniformly accelerated during the entire time. What net force is exerted on it?

Answers:You must first find the average acceleration : since there is acceleration there is a net force being applied acceleration=[velocity(final) - velocity(initial)]/time a=(35-0)/3 a=11.67 m/s Force=mass * acceleration F=m*a F=706 kg * 11.67m/s F=8237 N (newtons)

Question:5.5) a constsnt retarding force of 5oN is applied to a body of mass 20kg. moving initially with a speed of 15m/s.How long does the body take to stop? 5.6)a constant force acting on a body of mass 3kg changes its speed from 2m/s to 3.5 m/s in 25s.The direction of motion of the body remains unchanged.What is the magnitude and direction of the force? 5.7)a body of mass 5kg is accted upon by two perpendicular force4s 8N and 6N.Give the magnitude and direction of the acceleration of the body? 5.9)a rocket with a lift of mass 20000kg is blasted upwards with an initial acceleration of 5m/s^2.Calculate the initial force of the blast? 5.11)a truck starts from rest and accelerates uniformly at 2m/s^2.At t=10s,a stone is dropped by a person standing on the top of the truck(6m high from ground).What are the velocity and acceleration of the stone at t=11s?