Newton's Second Law of Motion Question?

a = 4m / s^2

Force = mass * acceleration

You can rearrange that equation however you need to to solve for the missing parameter.

In this case, you know the initial Force (63 N) and the acceleration (9 m/s^2). You put the knowns on the same side of the equation:

(63 N) / (9 m/sec^2) = mass = 7 kg

Now you have a new force on the same object (mass stays constant), so you have to rearrange the F=ma equation to put your knowns on the same side of the equation:

(28 N)/ (7 kg) = acceleration = 4 m/sec^2

If you're doing dimensional analysis, it would help to know that 1 N = (1 kg m)/sec^2. It helps as a double check to make sure you did your algebra correctly when you're moving your knowns to the same side of the equation.

well ... newton's second law states that the force is equal to the rate of cange of momentum

Momentum(M) is equal to the mass of the object multiplied by its velocity

So M = mass * velocity

and so .. Force = (mass * velocity ) / time .. - as force is equal to the rate of change of momentum-

and so we could say that Force = mass * (velocity/time)

and since that the velocity/time is the acceleration

We deduce that Force= mass * acceleration

considering the problem u r trying to solve

Force =63 N making acceleration = 9 m/s^2

by using the the equation F=ma

therefore mass of the object is 7 kg (63/9)

mass=7 kg

and so when the force on the body changes to 28N

therefore the acceleration of the object will be 4 m/s^2 (28/7)

again using the equation F=ma

F = m*a

Force = mass * acceleration

If the force is n times smaller, the acceleration will also be n times smaller F ~ a

In this case the objects acceleration will be 4 m/s^2

a=(28/63)*9 = 4 m/s^2

you know F = 63 and a = 9, then

F = m * a

shows that

m = F/a = 63 / 9 = 7 kg

The 28 N force leads to an acceleration of

a = F/m = 28 / 7 = 4 m/s^2

F=m*a

F=force

m=mass

a=acceleration

A newton ( N) = kg*m/s^2 where the 'm' here refers to meter, not mass.

F and a are given, solve for m.

m = F/a = 63 (kg*m/s^2)/9(m/s^2) = 7kg

In the second part of the problem, force is given and you have the mass from the first part of the problem. Solve for acceleration.

F=m*a

a=F/m=28N/7kg=4m/s^2

as F=m*a , 63=m*9.

so m=7kg. the mass of the object will remain constant.

so 28=7*a. therefor a=28/7 =4 m/s2

since the variation is direct

(28/63)*9=4 m/s/s

Force = mass * acceleration

Mass stays constant, so:

F1 = m * a1 -----> 63 [kg*m/sec^2] = m * 9 [m/sec^2]

F2 = m * a2 -----> 28 [kg*m/sec^2] = m * A

63/28 = 9 [m/sec^2] / A

A = 9*(28/63) [m/sec^2]

A = 4 [m/sec^2]

the problem is probably because the acceleration is 9.8 m/s/s, not just 9