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A rocket becomes progressively easier to accelerate as it travels toward space. Why is this so? (There are several reasons.) 1. The rocket becomes less massive as it is traveling toward space: it burns up its fuel, and the same force will accelerate it more because it has less weight. 2. As the rocket rises through the atmosphere, the density of air is less. There is less air resistance that the force of the rocket must overcome, and it will be easier to accelerate it. 3. Since the force due to gravity is a function of the size and the distance between two bodies, as the rocket gets further from Earth, there is less force due to gravity, and it becomes easier to accelerate the rocket.

A jet has a mass of 330,000 kg. Its engines thrust with 250,000 N of force. What is its acceleration?

Acceleration =

m force 250,000 N = = 0.75 2 s mass 330,000kg

The units of force are Newtons are When you divide by kg, you get 0.75

kg. m . s2

m s2

m s 2 , since it is 0.7575757575…, round the next 7 up to

Note: to round off m 8 to get 0.758 2 . If you want to use the line to represent the repeating s decimal, only write the pair of repeating digits once, and make the line over m both of them, because both repeat. Don’t write 0.7575 2 , because that s implies that the first two digits are not involved in the repeating answer.