How Do Forces Affect Motion in Different Scenarios?

[xgrape01]

1.

Homework Statement

Suppose a 66-kg boy and a 42-kg girl use a massless rope in a tug-of-war on an icy, resistance-free surface. If the acceleration of the girl toward the boy is 3.0 m/s2, find the magnitude of the acceleration of the boy toward the girl.

Homework Equations

Newton's Second Law of Motion?

The Attempt at a Solution

I tried to use Newton's Second Law but got a incorrect answer

2.

A 4570-kg helicopter accelerates upward at 1.8 m/s2. What lift force is exerted by the air on the propellers?
I did 4570/1.8 =2538.8888 N but that seems too big


3. An 880-kg (1945 lb) dragster, starting from rest, attains a speed of 26.0 m/s (58.2 mph) in 0.59 s.
(a) Find the average acceleration of the dragster during this time interval.
m/s^2

(b) What is the magnitude of the average net force on the dragster during this time?

N
(c) Assume that the driver has a mass of 68 kg. What horizontal force does the seat exert on the driver?
880-68 = 812?

 

[rock.freak667]

For the first one, the force pulling the girl is the opposite for the force pulling the boy. Newton's third law. Now use the second law.

2) Make an equation relating the upward forces and the downward forces and the resultant force it produces.

 

[tomcue]

I would like to point out that the content provided does not seem to be related to lift force and acceleration. The first two questions appear to be about force and acceleration in general, while the third question involves a dragster and its acceleration. Lift force, on the other hand, is a force that acts on an object in a fluid (such as air) in a direction perpendicular to the fluid flow. It is not clear how the provided content is related to lift force.

That being said, I will provide some guidance on the attempted solutions. For the first question, you are correct in using Newton's Second Law of Motion, which states that the net force on an object is equal to its mass multiplied by its acceleration. In this case, the net force on the girl is equal to her mass (42 kg) multiplied by her acceleration (3.0 m/s^2). This should give you the magnitude of the force that the boy is exerting on her.

For the second question, you are correct in using the same equation, but it seems like you may have made a calculation error. The correct answer should be 4570 x 1.8 = 8230 N, which is a reasonable value for lift force on a helicopter.

For the third question, you are correct in using the same equation to find the average acceleration of the dragster. However, for part (b), you need to use the equation F = ma, where F is the net force, m is the mass, and a is the acceleration. For part (c), you can use the same equation to find the horizontal force exerted on the driver by the seat. However, it is important to note that the driver's mass should not be subtracted from the dragster's mass, as they are two separate objects. Instead, you can use the driver's mass (68 kg) and the acceleration of the dragster to find the net force on the driver, and then use the same equation to find the horizontal force exerted by the seat.