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In this lesson, we will learn how to solve problems using Newton's first law.

Q1:

A body was moving uniformly under the effect of three forces F 1 , F 2 , and F 3 . Given that F i 1 = 7 and F j 2 = 8 , where i and j are orthogonal unit vectors, determine F 3 which ensures that it will move at a constant velocity.

Q2:

A car of mass 1.8 tonnes is moving at a constant speed on a horizontal road. If the resistance to the motion is 57.6 kg-wt per tonne of the car’s mass, find the force of its motor.

Q3:

A train of mass 50 tonnes has an engine whose maximum driving force is 9 000 kg-wt. Given that the resistance to its motion due to friction is directly proportional to the square of its speed and that this resistance was 20 kg-wt for each tonne of the train’s mass when its speed was 75 km/h, find the maximum speed of the train.

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