In order for you to jump a distance of 4 feet horizontally, you must exert a force of 200 N.
When you are standing on the ground, you have
no trouble doing this. If you are standing in a
canoe, however, and you need to jump 4 feet to
reach the pier, you will surely fall in the water
Why is it that you cannot jump 4 feet out of a
canoe when you can easily do this when on land?

Answertraveling around a circular trackexplanation"traveling around a circular track" is the best answer as you could be traveling around a circular track at a constant speed. your velocity would therefore have the same magnitude but will always be constantly direction. since acceleration is the rate of change of velocity, the rate of change will only involve the direction of velocity and not the magnitude.wrong choices: "an object at rest" does not accelerate at all"increasing speed while traveling around a curve" means that the acceleration will not be constant due to only change in direction; it will be constant due to both magnitude and direction"an object in free fall" does not necessarily change direction 

Answer(b) both involve the use of levers;