Why Do My Physics Calculations on Force and Acceleration Keep Going Wrong?

[buffgilville]

1) A mass 1.3 kilograms is pushed with a horizontal force 17.5 Newtons of a smooth inclined plane which bears an angle 12.5 to the horizontal. Find the acceleration of the mass (g = 9.81 m/s).

I got 2.12, but it was wrong, and I don't know why.

2) A mass 1.9 kilograms is pushed with a horizontal force 20 Newtons of a smooth inclined plane which bears an angle 27 to the horizontal. Find the distance the block moves in 6.5 seconds (g= 9.81 m/s2).

I got 198.13, but it was wrong, and I don't know why.

 

[marlon]

1) A mass 1.3 kilograms is pushed with a horizontal force 17.5 Newtons of a smooth inclined plane which bears an angle 12.5 to the horizontal. Find the acceleration of the mass (g = 9.81 m/s).

I got 2.12, but it was wrong, and I don't know why.

This is a matter (also for the second question) of using the right components of given forces. The given force is HORIZONTAL so you need the component of this force in the direction that the object moves: 12.5 degrees upwards.

F = ma so that a=F/m and F = 17.5*cos(12.5)

I get 13.1 m/s² for this one

Then there is gravity F =m*g pointing down vertically. The component of this force along the inclination is -m*g*sin(12.5). And minus because it points DOWN the y-axis...so the acceleration here is -2.1 m/s²

So I get : 13.1 - 2.1 = 11 m/s² as an anwser...

marlon

same thing for the second question : draw a sketch and call the inclination the x-axis...

 

[M98Ranger]

In both of these problems, it is important to understand the relationship between force, mass, and acceleration. The formula for calculating force is F=ma, where F is force, m is mass, and a is acceleration. In the first problem, we are given the mass, force, and angle of the inclined plane, and we are asked to find the acceleration. The correct formula to use in this situation is F=mg sinθ, where θ is the angle of the inclined plane. Plugging in the given values, we get F= (1.3 kg)(9.81 m/s^2) sin(12.5) = 2.12 N. Therefore, the acceleration is 2.12 m/s^2.

In the second problem, we are given the mass, force, and time, and we are asked to find the distance. To solve this, we can use the equation d= 1/2at^2, where d is distance, a is acceleration, and t is time. Plugging in the given values, we get d= 1/2(1.9 kg)(9.81 m/s^2)(6.5 s)^2 = 198.13 m. Therefore, the distance the block moves in 6.5 seconds is 198.13 meters.

It is important to carefully read and understand the given information in a problem and use the correct formula to solve it. If you are unsure why your answer is incorrect, double check your calculations and make sure you are using the correct formula. It can also be helpful to show your work and check your answer with someone else to catch any mistakes. Keep practicing and you will become more confident in solving problems involving force and acceleration.