Any lump of osmium is. Iridium and gold are also very close.
To develop this problem we will apply the concepts related to the kinematic equations of motion, specifically that of acceleration. Acceleration can be defined as the change of speed in an instant of time, mathematically this is

If a mobile is decreasing its speed (it is slowing down), then its acceleration is in the opposite direction to the movement. This would imply that the acceleration vector is opposite to the velocity vector.
Therefore the correct answer is B.
A car driving up a hill at a constant speed experiences no change in its kinetic energy while it's potential energy increases with increasing height, thus none of the options are correct.
Understanding the concept
Consider a car moving up the hill at a constant speed as shown in the figure below. The following forces act on the car:
- N is the normal reaction force acting in an upward direction
- f_s is the static friction force exerted due to friction between the road and the tires of the car
- f_k is the rolling friction force in the direction opposing that of the tire
- mg is the force acting in a downward direction.
- θ is the angle of inclination.
Here as the car is moving up the hill at a constant speed, the net force exerted on the car is zero. Also, the kinetic energy of the car will not change as its velocity is constant and the potential energy will change with increasing height. Thus, none of the given options are correct.
Learn more about motion on an incline here:
<u>brainly.com/question/13513083</u>
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Explanation:
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