What causes interstellar dust and gas to start to contract and form a protostar?

1) the shockwave from a supernova

2) nearby black hole

3) an increase in the solar wind

4) nuclear fusion

What is the maximum and minimum resultant possible from a 20-N force and 4-N force?

A train travels 53 kilometers in 4 hours, and then 90 kilometers in 3 hours. What is the average speed

A small model of a pump is tested in the laboratory and found to have a specific speed, nsd, equal to 1000 when operating at peak efficiency.

When studying atoms, scientists can ignore the blank force between charged particles that make up the atoms because it is many millions of times smaller than other forces in the atom

The acceleration of a particle moving only on a horizontal xy plane is given by, where is in meters per second-squared and t is in seconds. at t = 0, the position vector locates the paticle, which then has the velocity vector. at t = 2.

A heavy rope, 50 ft long, weighs 0.5 lb/ft and hangs over the edge of a building 120 ft high. how much work is done (in ft-lb) in pulling half the rope to the top of the building?

Does adding a neutron to an atom's nucleus makes it an ion?

What is the difference between a fault-block and upwarped mountains?

Which of the following is not one of the reasons to properly warm up before exercising? A. Develop overall flexibility. B. Increase blood flow to the muscles and raise body temperature. C. Prevent injuries such as strains sprains and muscle cramps.

you are not chilly when swimming in warm water. but when emerging from warm water on a warm summer day, you feel chilly if the wind is blowing. Explain