Question

1.The planet Venus orbits the sun in an almost perfect circle. It what direction is its acceleration? Its acceleration

-equals zero, since its speed is constant.

-points in the same direction as its velocity.

-points at right angles to its velocity, in toward the sun.

-points at right angles to its velocity, out away from the sun.

2.How does the work needed to stop the car compare with the energy it has while moving?

		Less work is needed than the amount of energy.
		The work must be the same as the amount of energy.
		The work must be more than the amount of energy.

3.Which takes more work, a car going from rest to 10 mi/hr or the same car going from 10 to 20 mi/hr?

		from rest to 10 mi/hr
		from 10 to 20 mi/hr
		both take the same work

Answer 1

(1) the acceleration points at right angle to the velocity, in towards the sun.

This acceleration is the centripetal acceleration due to Gravitational force.

(2) the work done must be same as the amount of energy.

(3) more work is done in going from 10 to 20 mi/h

Because in this case the change in kinetic energy is more.