One speed skater starts across a frozen lake at an average speed of 8 m/s. Ten seconds later, a second speed skater starts from
1 answer:
Answer:
40 s
Explanation:
After 10 seconds, the first skater would have a 8m/s * 10s = 80 m head start
Let t be the number of seconds after the second skater starts will the second skater overtake the first skater
The distance traveled by the first skater after t seconds is
Similarly the distance traveled by the 2nd skater after t seconds is
Since the 2nd skater catches up to the 1st one after 80 m behind, the distance traveled by the 2nd one must be 80m greater than the distance of the 1st skater
We can substitute
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where
W is the work
Kf is the final kinetic energy of the bus
Ki is the initial kinetic energy of the bus
Since the bus comes at rest, its final kinetic energy is zero:
, so the work done by the brakes to stop the bus is
And the work done is negative, because the force applied by the brake is in the opposite direction to that of the bus motion.
where
W is the work
Kf is the final kinetic energy of the bus
Ki is the initial kinetic energy of the bus
Since the bus comes at rest, its final kinetic energy is zero:
And the work done is negative, because the force applied by the brake is in the opposite direction to that of the bus motion.