An object is moving with an initial velocity of 4.0 m s–1 to the right. The velocity of the object changes so that its final velocity is 3.0 m s–1 downwards, as shown.
Which arrow represents the change in velocity of the object?
ANSWER: B
The Physics Behind
- The key idea here is vector addition.
- When adding quantities with direction e.g. velocities, a tip-to-tail method can be used.
- Represent each vector by an arrow with its magnitude proportional to length of arrow and direction represented by direction of arrow itself.
- With same scale, start drawing one starting from the tip of the previous [tip-to-tail].
- When done drawing all arrows, tip-to-tail, connect the tail of the first arrow drawn and tip of the last arrow using a straight arrow.
- its length is proportional to magnitude of the resultant or vector sum
- its direction is given by the arrow
- A change in a quantity e.g. change in velocity Δv, means final velocity v minus initial velocity u.
- You can rewrite Δv = v - u as Δv = v + (- u).
- Then use the tip-to-tail, that is, draw an arrow representing one vector and draw the next vector from its tip [consider the negative as you are adding a negative as suggested by the above formula].
- Your diagram should look like final velocity drawn downward with initial velocity drawn leftward i.e. + (-v).
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