Explanation:
The heart rate of the astronaut is 78.5 beats per minute, which means that the time between heart beats is 0.0127 min. This will be the time t measured by the moving observer. The time t' measured by the stationary Earth-based observer is given by

a) If the astronaut is moving at 0.480c, the time t' is


This means that time between his heart beats as measured by Earth-based observer is 0.0145 min, which is equivalent to 69.1 beats per minute.
b) At v = 0.940c, the time t' is


So at this speed, the astronaut's heart rate is 1/(0.0372 min) or 26.9 beats per minute.
Answer:
Force of static friction between the two surfaces
Explanation:
When two surfaces come into contact, they exert a force that resist the sliding of the two surfaces. This force is called static friction.
This force is given by the relation

Where,
μ - coefficient of static friction
η - normal force acting on the body
When a force acts on a body placed on a rough surface, it doesn't do any work if the applied force was less than the force of static friction.
So, in order to move the body, the applied force should be greater than the force of static friction.
Answer:
mechanical energy to heat energy to chemical energy
It would be B, like charges repel and unlike charges attract.
Answer: "B" Changing Position
Great Question!
Explanation: <u><em>When a ball bounces to the ground it hits the ground with some energy. The amount of energy with which it hits the ground is kinetic energy. When it comes in the contact with the ground kinetic energy gets converted into potential energy. This potential energy again gets converted into kinetic energy and balls moves again from the ground and bounces multiple times. So, the ball ends up changing position</em></u>
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