Relative speed of Tina with respect to David is given by



now the acceleration of Tina with respect to David



now the relative displacement would be zero when Tina cross David
so now we have



now the speed of Tina at this moment is given as



<em>so the speed will be 52 m/s</em>
If the object has a lower density than water, it will float.
If the object has a higher density than water, it will sink.
The answer is B. Sunlight (white light) refracts when it passes through droplets of water in the atmosphere
The scalar operates only on the magnitude of the vector.
So the length of the vector may change ... becoming longer
or shorter ... but its direction doesn't change.
I'm not sure but for the first one, if there were more electrons than protons that would mean the object would have a positive charge so you could put another object that is positively charged near it, to see if it would attract and if it would it would mean it's negatively charged and if it wouldn't it would mean it's positively charged. (not sure)
for the second one, after you've rubbed the balloon oh hair, the electrons from your hair have transferred onto the balloon, meaning that the balloon is now negatively charged. because the wall is neutral, it means that it has the SAME number of both protons and electrons ( positive and negative charges cancel out to create a neutral charge). because the protons are positively charged, and the balloon is negatively charged, the two objects will attract because opposite charges attract. this happens because of static electricity.
hope this helps :)