A mechanical wave such as sound needs a medium to travel through. This is why they say that in space, no one can hear you scream (because space is a vacuum and no medium exists). On the contrary, light can exist in wave or particle form. This is why we have the ability to see beyond the realms of the Earth.
I DONT know FiGURE it out YOURSELF
The child's linear speed is
<em> (pi / 5) x (the child's distance from the center of the ride, in feet)</em>
feet per second.
Don't know if this is a True/False questions but that is true
Work done by a given force is given by

here on sled two forces will do work
1. Applied force by Max
2. Frictional force due to ground
Now by force diagram of sled we can see the angle of force and displacement
work done by Max = 

Now similarly work done by frictional force



Now total work done on sled

