Vectors and Acceleration in a Straight Line

In summary, the change in velocity when 6.0 m/s becomes -15 m/s is -9 m/s with 180 degrees change in direction. When 5.0 m/s East becomes 15 m/s West, the change in velocity is 9 m/s with a change in direction from 90 degrees to 270 degrees. For the baby buggy rolling down a ramp, the average velocity is 3 m/s and the final velocity at the bottom is 6 m/s with an acceleration of 1.2 m/s^2. To calculate the final velocity without knowing the acceleration, you can use the formula s = t(u+v)/2.
  • #1
Peter G.
442
0
What is the change in velocity when:
a) 6.0 m/s becomes - 15 m/s
b) 5.0 m/s East becomes 15 m/s West

My doubt is mainly the notation: How I should answer, here is my try:

a) -9 m/s with 180 degrees change in direction
b) 9 m/s with from direction bearing 90 degrees to 270 degrees

And: A baby buggy rolls down a ramp which is 15 m long. It starts from rest and accelerates uniformly and takes 5.0 seconds to reach the bottom:
a) Average Velocity: 15 /5 = 3 m/s

Now, b asks for the velocity at the bottom. I don't know how to calculate the velocity without the acceleration, which is asked in question c)

c) s = ut x 1/2at^2
a = 1.2 m/s^2

and then

b) v = u + at
v = 6 m/s

Anyone can teach me how to get the velocity without the acceleration and with the notation in the first question?

Thanks,
Peter
 
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  • #2
You can find the final velocity with this formula (only when acceleration is constant):

s = t(u+v)/2
 
  • #3
Aw, yea that's right, thanks.

And what about my answers to the first question? Think they are O.K?
 

1. What is a vector in physics?

A vector in physics refers to a quantity that has both magnitude and direction. It is represented by an arrow pointing in the direction of its magnitude and the length of the arrow represents the magnitude of the vector.

2. How is velocity related to acceleration in a straight line?

Velocity and acceleration are closely related in a straight line. Acceleration is the rate of change of velocity, so any change in the velocity of an object will result in acceleration. In other words, acceleration is the derivative of velocity with respect to time.

3. Can acceleration be negative?

Yes, acceleration can be negative. Negative acceleration, also known as deceleration, occurs when the velocity of an object decreases over time. This can happen when an object is slowing down or changing direction.

4. How is acceleration calculated?

Acceleration is calculated by dividing the change in velocity by the change in time. It is represented by the formula a = (vf - vi)/t, where a is acceleration, vf is final velocity, vi is initial velocity, and t is time.

5. What is the difference between average and instantaneous acceleration?

Average acceleration is the change in velocity over a specific time interval, while instantaneous acceleration is the acceleration at a specific moment in time. Average acceleration can be calculated by dividing the change in velocity by the change in time, while instantaneous acceleration can be calculated by taking the derivative of the velocity function with respect to time.

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