Answer:
2000J
Explanation:
work done = force * distance
Work done = 100 * 20
Work done = 2000J
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The grommets on your shoe (Holes through which you place the lace) act as the pulley. When you tighten at the top it restricts at the bottom and compresses around your foot.
The same can be applied to a pulley; If you have the proper set up Pulling one string causes two actions; the first being the most obvious. And the second being its effect. The Grommets of your shoe are the pulley's; while your Shoelaces are just the rope with which you operate the pulley.
Astronomers can measure a star's<span> position once, and then again 6 months later and </span>calculate<span> the apparent change in position. The </span>star's<span> apparent motion is called stellar </span>parallax<span>. The </span>distance<span> d is measured in parsecs and the </span>parallax<span> angle p is measured in arc seconds.</span>
The braking distance is given by 
Explanation:
When the driver of a car hits the pedal of the brakes, the car starts decelerating until it stops. Assuming the deceleration is constant, then the motion is a uniformly accelerated motion, so we can use the following suvat equation:
where
u is the initial speed of the car
v is the final speed of the car, which is zero because the car comes to rest:
v = 0
a is the acceleration of the car
s is the distance travelled by the car during the deceleration, so it is the braking distance
Therefore, re-arranging the equation for s, we find an expression for the braking distance:
Note that the sign of 
is negative since the car is decelerating, therefore the final sign of 
is positive.
Learn more about accelerated motion:
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