Question

Which is not expecting acceleration?
A point on the outside of a spinning top whose rotational speed is constant.
A skydiver whose air resistance is equal to that of her weight.
A car on the freeway experiencing a net force of -120 N.
A submerged beach ball whose buoyant force is eight times the force of gravity on it.
Which is a valid internal frame of reference?

A frictionless spinning merry go round.

A falling rock.

A hot air balloon moving at 30 degrees east of north with no net force.

A space shuttle whose boosters just ignited for takeoff.

Two teams are playing tug of war. The team on the right is pulling with 4320 N. The team on the left is pulling with 4380 N. Which direction does the rope move and with what force?

60N to the right
120N to the left
60 N to the left
120 N to the right

Answer 1

#1)

1).  A point on the outside of a spinning top whose rotational speed is constant.

It will not accelerate as its net speed is ZERO

2).  A skydiver whose air resistance is equal to that of her weight.

Since weight is counterbalanced by resistance so here net force is zero so acceleration must be zero here

3).   A car on the freeway experiencing a net force of -120 N.

Since there it acts net force F = -120 N so it will accelerate here

4).  A submerged beach ball whose buoyant force is eight times the force of gravity on it.

Since buoyant force is more than weight of the ball so it will accelerate upwards

#2)

A non accelerating fra me is always a valid inertial frame

A frictionless spinning merry go round.

(since it is having centripetal acceleration so it is non inertial frame)

A falling rock.

(Since it is falling with acceleration a = 9.8 m/s^2 so it is non inertial)

A hot air balloon moving at 30 degrees east of north with no net force.

(Since net force on hot air balloon is ZERO so it is Inertial Frame)

A space shuttle whose boosters just ignited for takeoff.

(Since space shuttle ignite the boosters so it will accelerate here and hence it is non inertial)

#3

here two forces given as

$F_1 = 4320 N$ towards right

$F_2 = 4380 N$ towards Left

Since left side applied force is more than right side applied force so net force on it will be towards Left and it is given by

$F = 4380 - 4320 = 60 N$

So it is 60 N Left

Answer 2

Answer:

1. A submerged beach ball whose buoyant force is eight times the force of gravity on it.

2. A hot air balloon moving at 30 degrees east of north with no net force.

3. 60 N to the left

Explanation:

1. A submerged ball is not expecting any form of acceleration. This is because there is no form of motion on it. The only forces that are experienced on the ball are the compressing forces from the water.

2. A hot air balloon will be a good point of reference. This is because it has no definite direction of movement or acceleration.

3. The sum of the forces will be:

$3280 - 3220 = 60$

so the resultant force will be 60 N to the left.