Physics Tip:
Kinematics – How to interpret a velocity-time graph well
Our IP Physics guru Lisa would like to offer a tip on kinematics today. This is relevant regardless whether you are taking IP or the ‘O’ Levels.
A common question is to describe the motion of the velocity-time graph in the graph.
Steps to take:
Always look out for key points in time when the motion changes, label the parts as shown by A to F in the graph.
1. Decide the direction for positive velocity: forward direction
2. Locate the part of the graph to describe: AB
3. Observe if the velocity is increasing or decreasing: Increasing for AB
4. Conclude that increasing velocity is acceleration & decreasing velocity is deceleration: Accelerating for AB
5. Observe if the gradient of the curve is positive or negative: Positive for AB
6. Observe if the gradient of the curve is increasing or decreasing, to conclude if the curve is increasing acceleration of decreasing acceleration: Decreasing acceleration for AB
Combine the above step into the final answer.
Answer:
From A to B, the object moves forward with a decreasing acceleration,
from B to C, the object continues forward with increasing acceleration,
from C to D, the object moves briefly with constant velocity before continuing forward with increasing deceleration,
from D to E, the object moves backward with decreasing acceleration and
from E to F, the object continues backward with increasing deceleration and
finally comes to rest at F.
The object did not go back to the starting position as the area under the graph for the curve above the x-axis (which represents displacement) is greater than the area under the graph for the curve below the x-axis.
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Lisa teaches upper secondary IP Physics at Study Room on Wed and Fri evenings. If you have a preferred timeslot, you may PM/DM us to form a new class too. #physics from Study Room https://ift.tt/38Jppqj