1. A wind-up car has a mass of 0.40 kg. The wind-up car is accelerating at 0.40 m/s2. What is the net force acting on the wind-up car? 0.40 N
1.0 N
0.16 N
10 N

2. A toy train has an acceleration of 1.2 m/s2. A net force of 3.0 N is acting on the train. What is the mass of the train?

3.6 kg
0.4 kg
2.5 kg
4.0 kg

What is the orbital period of a spacecraft in a low orbit near the surface of mars? the radius of mars is 3.4×106m.

An charge with mass m and charge q is emitted from the origin, (x, y)=(0,0). a large, flat screen is located at x=l. there is a target on the screen at y position y(h), where y(h) > 0. in this problem, you will examine two different ways that the charge might hit the target. ignore gravity in this problem. 1.assume that the charge is emitted with velocity v(0) in the positive x direction. between the origin and the screen, the charge travels through a constant electric field pointing in the positive y direction. what should the magnitude e of the electric field be if the charge is to hit the target on the screen? express your answer in terms of m, q, y(h), v(0), and l. 2.now assume that the charge is emitted with velocity v(0) in the positive y direction. between the origin and the screen, the charge travels through a constant electric field pointing in the positive x direction. what should the magnitude e of the electric field be if the charge is to hit the target on the screen? express your answer in terms of m, q, y(h), v(0), and l.

What is the efficiency of an engine that does 80 j of work and exhausts 320 j of heat while taking in 400 j of heat ? a. 10% b. 20% c. 80% d. 25%