Help please?

Question

1. Explain why free-fall acceleration can be regarded as a constant for objects falling within a few hundred miles of Earth's surface.


2.Calculate the mass in kg of an object that wieghs 1225 N on Earth.


3.Apply Newtons first and second laws to expalin why an object moving in a circular path at a constant speed is undergoing acceleration and has a force exerted on it.

4.Determine the force needed to accelerate a 1357 kg car forward at 8.0 m/s^2.

5. Indicate which of the following has greater momentum: a 500 kg car moving at 64 km/h, a 250 kg cart moving at 128 km/h, or a 1000kg truck moving at 32 km/h.

please help at least anwser one please i'm begging

Answer 1

OK a little homework help;

1. Gravity 'pulls' at 32ft/s^2 at the surface. The higher you go, the less gravity has an effect. To find the rate of acceleration from very high altitudes, you would need to integrate 32ft/s^2 from max altitude to zero.

Oddly enough, since gravity is proportional to mass, the gravity is at maximum at the surface. As you leave the surface of earth, gravitational pull gets less. AND, as you go to the center of the earth, gravitational pull becomes less again. In fact, when you are at the center of the earth, you would weigh zero pounds.

2, mass x acceleration = force.
so, mass = force / acceleration
mass = 1225 N / 9.8 m/s

5. momentum = mass x velocity so;
500 x 64, 250 x 128, 1000 x 32 - which is larger

4. force = mass x acceleration = 1357 x 8

3.
Law I. Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.

Law II. The relationship between an object's mass m, its acceleration a, and the applied force F is F = ma.

Answer 2

1. It depends on your tolerance for error. The earth's radius is just under 4000 miles. The equation for gravitational attraction involves the square of the distance to the center of the earth.

4000^2 = 16,000,000
4200^2 = 17,640,000

If a discrepancy of that percentage is no problem, then ya, I guess you can say that.

2. W = m*g
m = W/g where g = 9.8 m/s^2

3. Newton's 1st: That object would go in a straight line if it didn't have an net force acting on it. It's not going in a straight line, therefore it has an net force F on it.

Newton's 2nd: The object with net force F on it undergoes acceleration according to F = m*a.

4. F = m*a

5. Momentum is m*v. Multiply and compare.

Answer 3

#1...would be gravity.
#2...a Newton = 1 kg m/s^2.....so 1225 N / 9.8 m/s^2 = 125 kg.
dont know 3 sorry
#4...F = ma...so F = 1357(8.0) = 10856 N
#5...just use F = ma to find which is greatest

Answer 4

Do your own homework. You can't bring Yahoo Answers with you to the test!

Answer 5

If this is homework talk to your teacher or maybe a parent or friend can help
GOOD LUCK HUN!!!!
I know them but it would be cheating