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Physics Homework

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1. You push a heavy car by hand. The car, in turn, pushes back with an opposite but equal force on you. Doesn’t this mean the forces cancel one another, making acceleration impossible? Why or why not?

-No, because of the system that is involved. The system would be you and the heavy car, therefore the action and reaction forces are internal and cancel out.

2. If you stand next to a wall on a frictionless skateboard and push the wall with a force of 30N, how hard does the wall push on you? If your mass is 60 kg, what is your acceleration?

30 N
-This I am not too sure how to do it. would you have to multiply 60kg and 30N?

3. When a rocket engine is above the Earth’s atmosphere, what does it push on to cause acceleration?

-The rocket recoils causing it to accelerate dude to the reaction forces that are exerted by the material the rocket fires.

5. A truck has a trailer attached. As the truck drives off it exerts a force on the trailer that tends to pull the trailer along. But, according to Newton's 3rd Law, the trailer exerts an equal and opposite force on the truck which tends to stop the truck. How, then, can the truck and trailer accelerate and drive off?

-There is a system involved where there is an external force happening when the road pushes on the trailer that's when the truck and trailer accelerates and drives off.

  • Physics Homework -

    2. The forces cancel, so the net force is zero, and the acceleration is zero (f=ma).
    Yes on 3. Newtons third law. There is no pushing against anything.

    5. actually, the road is opposing the motion (friction). The net force of the tire on the road is greater than frcition opposing motion, and the truck acceleraltes. The truck-trailer force pair is internal, and cancels.

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