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
To determine which scenario does not expect acceleration, let's analyze each option:
1. A point on the outside of a spinning top whose rotational speed is constant.
Explanation: In this scenario, the point on the outside of the spinning top is experiencing circular motion. Although the speed is constant, the direction of the velocity is changing, and therefore, there is acceleration.
2. A skydiver whose air resistance is equal to that of her weight.
Explanation: When a skydiver reaches terminal velocity, their weight is balanced by the air resistance acting against their motion. At this point, the skydiver experiences zero net force and hence no acceleration.
3. A car on the freeway experiencing a net force of -120 N.
Explanation: If the car is experiencing a net force of -120 N, it means there is a force acting in the opposite direction of its motion. This force will cause the car to decelerate or accelerate negatively, resulting in negative acceleration.
4. A submerged beach ball whose buoyant force is eight times the force of gravity on it.
Explanation: When the buoyant force acting on an object submerged in a fluid is greater than the object's weight, it experiences buoyant upward acceleration. Hence, the beach ball will accelerate upwards.
Therefore, the option that does not expect acceleration is: A car on the freeway experiencing a net force of -120 N.
Moving on to the next question,
To determine a valid internal frame of reference, let's analyze each option:
1. A frictionless spinning merry go round.
Explanation: In this scenario, the internal frame of reference is valid. Since the merry-go-round is frictionless, there are no external forces acting on it, allowing it to serve as a reference frame within itself.
2. A falling rock.
Explanation: A falling rock is not a valid internal frame of reference because it is subjected to the force of gravity and accelerates downward.
3. A hot air balloon moving at 30 degrees east of north with no net force.
Explanation: A hot air balloon moving at a constant velocity with no net force does not represent an internal frame of reference. It is still affected by external forces such as air resistance and gravity.
4. A space shuttle whose boosters just ignited for takeoff.
Explanation: Similar to the hot air balloon example, a space shuttle with ignited boosters is not an internal frame of reference. It is subjected to the force of thrust produced by the boosters and other external forces.
Therefore, the option that represents a valid internal frame of reference is: A frictionless spinning merry go round.
Lastly, for the question about the tug of war,
To determine the direction and magnitude of the force on the rope, we need to calculate the net force.
Given that the right team is pulling with 4320 N and the left team is pulling with 4380 N, we subtract the force on the right team from the force on the left team:
Net force = Force on the left team - Force on the right team
Net force = 4380 N - 4320 N
Net force = 60 N
Since the net force is 60N, the direction of the force on the rope will be in the direction of the left team's pull, and the magnitude will be 60N.
Therefore, the answer is: 60N to the left.
A skydiver whose air resistance is equal to that of her weight.
No net force so 0 = m a
No net force is a pretty strong hint
Oh come on you can do the tug of war.