An engineer in a locomotive sees a car stuck on the track at a railroad crossing in front of
the train. When the engineer first sees the
car, the locomotive is 320 m from the crossing
and its speed is 10 m/s.
If the engineer's reaction time is 0.73 s,
what should be the magnitude of the mini-
mum deceleration to avoid an accident?
Answer in units of m/s2.

Afisherman notices that his boat is moving up and down periodically without any horizontal motion, owing to waves on the surface of the water. it takes a time of 2.20 s for the boat to travel from its highest point to its lowest, a total distance of 0.670 m . the fisherman sees that the wave crests are spaced a horizontal distance of 5.80 m apart. (a) how much is the wavelength? (b) find the period of the wave. (c) how fast are the waves traveling? (d) what is the amplitude a of each wave?

If forces acting on an object are unbalanced. true or false

The mass of the sun is 1.99×1030kg and its distance to the earth is 1.50×1011m. what is the gravitational force of the sun on the earth?