4. How do scientists know that dark matter exists? (1 point) O They assume that anything invisible has to be dark.
O Something has to be there to form superclusters.
The Redshifts give the dark matter away.
O They observe gravitational lensing bending the light of other objects in space.

Aball is thrown straight up into the air with a speed of 21 m/s. if the ball has a mass of 0.1 kg, how high does the ball go? acceleration due to gravity is g = 9.8 m/s^2. a. 22.5 m b. 20.0 m c. 25.0 m d. 17.5 m

What you see with your eyes is a form of energy. a. light b. heat c. chemical d. electrical

Asailboat is traveling to the right when a gust of wind causes the boat to accelerate leftward at 2.5m/s2 for 4s. after the wind stops, the sailboat is traveling to the left with a velocity of 3.0m/s.assuming the acceleration from the wind is constant, what was the initial velocity of the sailboat before the gust of wind? answer using a coordinate system where rightward is positive.