Apacking crate with mass 80.0 kg is at rest on a horizontal, frictionless surface. at t = 0 a net horizontal force in the +x-direction is applied to the crate. the force has a constant value of 80.0 n for 12.0 s and then decreases linearly with time so it becomes zero after an additional 6.00 s. what is the final speed of the crate, 18.0 s after the force was first applied?

Final speed of the crate is 15 m/s

Explanation:

As we know that constant force F = 80 N is applied on the object for t = 12 s

Now we can use definition of force to find the speed after t = 12 s

so here we know that object is at rest initially so we have

Now for next 6 s the force decreases to ZERO linearly

so we can write the force equation as

now again by same equation we have

put t = 6 s

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