Acceleration is the rate at which an object changes its velocity. It defines how much the velocity is changing. The acceleration can be negative and positive. Negative acceleration is when the object slows down, while positive while the object goes faster.
<span>A ball moving at a constant speed around a circular track produces acceleration. </span>
This question is based on the fundamental assumption of vector direction.
A vector is a physical quantity which has magnitude as well direction for its complete specification.
The magnitude of a physical quantity is simply a numerical number .Hence it can not be negative.
A negative vector is a vector which comes into existence when it is opposite to our assumed direction with respect to any other vector. For instance, the vector is taken positive if it is along + X axis and negative if it is along - X axis.
As per the first option it is given that a vector is negative if its magnitude is greater than 1. It is not correct as magnitude play no role in it.
The second option tells that the magnitude of the vector is less than 1. Magnitude can not be negative. So this is also wrong.
Third one tells that a vector is negative if its displacement is along north. It does not give any detail information about the negativity of a vector.
In a general sense we assume that vertically downward motion is negative and vertically upward is positive. In case of a falling object the motion is vertically downward. So the velocity of that object is negative .
So last option is partially correct as the vector can be negative depending on our choice of co-ordinate system.
Answer: find the answer in the explanation as kinetic energy converts to potential energy.
Explanation:
Before the truck driver sees a dog running into the road, The mechanical energy state of the truck will be kinetic energy at maximum.
Immediately he applied the brakes, the mechanical energy of the truck will be combination of kinetic energy and potential energy.
The kinetic energy will gradually decrease as potential energy continue to increase till it reaches maximum potential energy.
The truck will come to a stop at maximum potential energy
