# Linear motion and Newtons law

• tattersfield
In summary, the conversation revolves around a question about a crane needing a force of 3kN to lift a mass of 6 tonne and determining the time it takes to lift the load. The participants discuss the use of kinematic equations and suggest finding the acceleration of the mass using Newton's second law to calculate the time taken to reach a velocity of 5m/s. They also acknowledge that the question is not well posed and offer further assistance if needed.
tattersfield

## Homework Statement

hi there, really don't know how to attempt this, could someone please give guidance, thanks. a crane needs a force of 3kN to lift a mass of 6 tonne. if the load is initially at rest and the maximum velocity is 5m/s, determine the time taken to lift the load. Any help would b great, been on with this for 2 days now. thanks

## The Attempt at a Solution

Lift it how far? Or is it the time taken for the crane to accelerate the load to 5m/s?

im not sure, that is the question , just how i got it, i don't understand it at all

Well I'd imagine you have to calculate the time it takes to reach its maximum speed. Do you know of the kinematic equations?

no i am brand new to physics, do you know of a good site that coulld explain it to me? thank you for answering

Ok there are a list of the kinematic equations here:

https://www.physicsforums.com/showpost.php?p=905663&postcount=2

What you'll need to do is find the acceleration of the mass due to the force from the crane using Newtons second law. Once you have the acceleration you can put it into on of the kinematic equations to find the time taken to accelerate to 5m/s.

Like I say before the question isn't posed particularly well so I'm not surprised you're confused. Have a go anyway and if you need more assistance just ask.

## 1. What is linear motion?

Linear motion, also known as rectilinear motion, is the movement of an object in a straight line. This can be in either a horizontal or vertical direction.

## 2. What is Newton's first law of motion?

Newton's first law of motion, also known as the law of inertia, states that an object at rest will remain at rest and an object in motion will remain in motion at a constant velocity, unless acted upon by an external force.

## 3. How does Newton's second law of motion relate to linear motion?

Newton's second law of motion states that the force applied to an object is equal to the mass of the object multiplied by its acceleration. In the context of linear motion, this means that the acceleration of an object is directly proportional to the force applied and inversely proportional to the mass of the object.

## 4. What is the difference between speed and velocity in linear motion?

Speed is a measure of how fast an object is moving, while velocity is a measure of how fast and in what direction an object is moving. In linear motion, both speed and velocity are measured in units of distance per unit of time (such as meters per second).

## 5. How does friction affect linear motion?

Friction is a force that opposes motion and acts in the opposite direction of an object's velocity. In linear motion, friction can slow down or even stop an object's movement if it is strong enough to counteract the applied force. It can also cause an object to change direction or experience a decrease in speed.

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