Question

A sky diver is falling through air, and the forces on him are air resistance 1400 N upward and gravity 2200 N downward. What is the magnitude of the net force acting on him?

329 N
800 N
3200 N
11,760 N
What is the mass of the skydiver?

91.6 kg
120 kg
210 kg
224.5 kg

What is the acceleration of him?
3.56 m/s2
5.3 m/s2
15.7 m/s2
35.6 m/s2

Answer 1

Fresultant = - 800 [N]

m = 224.26 [kg]

a = 3.56 [m/s²]

Step-by-step explanation:

The resulting force can be determined by the arithmetic difference of the air resistance force and the gravity force.

`F_(resultant)=F_(air)-F_(gravity)\\F_(resultant)=1400-2200\\F_(resultant)=-800[N]`

The negative sign of the result means that the force is directed downwards.

The mass can be easily calculated using the definition of the weight of the body. Where the weight is equal to the product of mass by gravitational acceleration.

`W =m*g\\`

where:

m = mass [kg]

W = weight = 2200 [N]

g = gravity acceleration = 9.81 [m/s²]

`m=W/g\\m=2200/9.81\\m= 224.26 [kg]`

Finally, acceleration can be calculated using Newton's second law which tells us that the resulting force on a body is equal to the product of mass by acceleration.

`F_(resultant)=m*a\\-800 = - 224.26*a\\a=3.56 [m/s^(2) ]\\`

The positive sign of acceleration tells us that effectively the body moves down.