Question

The velocity of an object decreases at a constant rate. The type of motion described is:
a) Non-uniformly retarded motion
b) Uniform motion
c) Non-uniformly accelerated motion
d) Non-uniform motion

Answer 1

Answer:

C) Non-uniformly accelerated motion

Explanation:

The acceleration is defined as

dv⃗ dt=a⃗

I you mean with "decreasing" that v=|v⃗ | decreases at a constant rate, then a=|a⃗ |=a0 and the integration of the first equation leads to

v(t)=−a0t+v0

with a0>0 and v0 some initial velocity.

From this it is easy to see that for fixed time intervals Δt=t2−t1 the change of velocity Δv is always the same regardless of t1,t2 as long as Δt remains fixed. The motion is indeed uniform acceleration.

However, the acceleration takes into account how the velocity-vector changes. Hence changing direction is also due to an acceleration. Take the uniform circular motion, the length of the vector v⃗ stays everywhere the same but there is an acceleration due to the constant changing of the direction of this vector. This is also uniform acceleration as the the direction of a⃗ changes, but its length remains fixed.

Answer 2

Answer:

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