6. A car experiences a forward engine force of 2000N. The combined frictional forces acting on the car are 600 N. If the car is accelerating at 3.0m/s, what is the mass of the car?
Ans: 467 kg
(I need the equation and work of it!!!)

As part of your daily workout, you lie on your back and push with your feet against a platform attached to two stiff springs arranged side by side so that they are parallel to each other. when you push the platform, you compress the springs. you do an amount of work of 79.0 j when you compress the springs a distance of 0.230 m from their uncompressed length. (a) what magnitude of force must you apply to hold the platform in this position? (b)how much additional work must you do to move the platform a distance 0.230 m farther? (c) what maximum force must you apply to move the platform a distance 0.230 m farther?

If a hiker that weighs 600 newtons climbs a 50 meter hill, how much gravitational potential energy has the hiker gained?

How much energy will be transferred to your eardrum while listening to this sound for 1.0 min?