1
Physics Notes:
Class 11:
Topic: Circular Motion.
1) Geo-Stationary satellite completes one rotation around the Earth in?
• 3hours
• 6hours
• 12hours
• 24hours
Answer: 24hours
Reason: It moves with same speed as of the Earth’s rotation. So, it completes one rotation in
24hours.
2) What is the apparent weight of a pilot with mass 60kg? If his plane accelerating
upwards with 4kg?
• 600 N
• 1000 N
• 3000 N
• 5000 N
Answer: 3000 N
Reason: T = mg + ma
m (g + 4g) = 5mg
5 × 60 × 10 = 3000 N
3) The direction of linear velocity for an object moving in a circular is?
• Directed away from the center.
• Directed towards the center.
• Along the tangent.
• Along the axis of rotation.
Answer: Along the tangent
Reason: Linear velocity is along the tangent of rotation and also known as tangential velocity.
4) If a body is falling freely in space, the mass of object placed in that body will be?
• Greater than its mass on Earth.
• Lesser than its mass on Earth.
• Zero.
• Equal to its mass on the Earth.
Answer: Equal to its mass on the Earth.
, 2
Reason: Weight is affected by free fall motion. Mass is constant.
5) When does an artificial Earth satellite that is in an artificial orbit experience its
greatest centripetal acceleration?
• When it first enters orbit.
• When it is nearest the Earth.
• Its centripetal acceleration is
always the same.
• When it is farthest from the
Earth.
Answer: When it is nearest the Earth.
Reason: The satellite travels at essentially the same velocity in its orbit, although its speed
does increase at its closest approach to the Earth. The distance from the satellite to the Earth
also changes while the satellite orbits the Earth. The closer approach to the Earth decreases
the radius of the orbit, which in turn causes an increase in the centripetal acceleration.
6) For moon revolving around the Earth the necessary acceleration is provided by?
• Frictional Force.
• Coulomb Fore.
• Gravitational Force.
• Tension Force.
Answer: Gravitational Force.
7) If we whirl a stone at the end of a string in the vertical circle, it is likely to break when
the stone is?
• At the highest point.
• At the lowest point.
• At any point during motion.
• At the point where gravity is not acting.
Answer: At the lowest point.
Reason: At the bottom of the circle, the ball is being pulled down by gravity. This means
that the string has to try to support this weight. The string will feel a force pulling it down.
At the same time, the ball is also being pulled up towards the center of the circle by the
centripetal force. By Newton’s third law, if the ball is pulled up by the string, the string will
be pulled down by the ball. So, the total net force acting on the string, is the sum of two
forces. This force is bigger than the weight of the ball alone, so maybe the string will snap.
It is at the bottom of the swing that the string has the greatest chance of snapping if it is not
strong enough.
8) Two disks of equal mass but different diameter is connected with an axle system that
allows them to roll down an incline together. Both disks start & finish at the same
time. Which of the following statements best describes the disks?
• Large disk has larger angular acceleration.
• Smaller disk has larger angular acceleration.
Physics Notes:
Class 11:
Topic: Circular Motion.
1) Geo-Stationary satellite completes one rotation around the Earth in?
• 3hours
• 6hours
• 12hours
• 24hours
Answer: 24hours
Reason: It moves with same speed as of the Earth’s rotation. So, it completes one rotation in
24hours.
2) What is the apparent weight of a pilot with mass 60kg? If his plane accelerating
upwards with 4kg?
• 600 N
• 1000 N
• 3000 N
• 5000 N
Answer: 3000 N
Reason: T = mg + ma
m (g + 4g) = 5mg
5 × 60 × 10 = 3000 N
3) The direction of linear velocity for an object moving in a circular is?
• Directed away from the center.
• Directed towards the center.
• Along the tangent.
• Along the axis of rotation.
Answer: Along the tangent
Reason: Linear velocity is along the tangent of rotation and also known as tangential velocity.
4) If a body is falling freely in space, the mass of object placed in that body will be?
• Greater than its mass on Earth.
• Lesser than its mass on Earth.
• Zero.
• Equal to its mass on the Earth.
Answer: Equal to its mass on the Earth.
, 2
Reason: Weight is affected by free fall motion. Mass is constant.
5) When does an artificial Earth satellite that is in an artificial orbit experience its
greatest centripetal acceleration?
• When it first enters orbit.
• When it is nearest the Earth.
• Its centripetal acceleration is
always the same.
• When it is farthest from the
Earth.
Answer: When it is nearest the Earth.
Reason: The satellite travels at essentially the same velocity in its orbit, although its speed
does increase at its closest approach to the Earth. The distance from the satellite to the Earth
also changes while the satellite orbits the Earth. The closer approach to the Earth decreases
the radius of the orbit, which in turn causes an increase in the centripetal acceleration.
6) For moon revolving around the Earth the necessary acceleration is provided by?
• Frictional Force.
• Coulomb Fore.
• Gravitational Force.
• Tension Force.
Answer: Gravitational Force.
7) If we whirl a stone at the end of a string in the vertical circle, it is likely to break when
the stone is?
• At the highest point.
• At the lowest point.
• At any point during motion.
• At the point where gravity is not acting.
Answer: At the lowest point.
Reason: At the bottom of the circle, the ball is being pulled down by gravity. This means
that the string has to try to support this weight. The string will feel a force pulling it down.
At the same time, the ball is also being pulled up towards the center of the circle by the
centripetal force. By Newton’s third law, if the ball is pulled up by the string, the string will
be pulled down by the ball. So, the total net force acting on the string, is the sum of two
forces. This force is bigger than the weight of the ball alone, so maybe the string will snap.
It is at the bottom of the swing that the string has the greatest chance of snapping if it is not
strong enough.
8) Two disks of equal mass but different diameter is connected with an axle system that
allows them to roll down an incline together. Both disks start & finish at the same
time. Which of the following statements best describes the disks?
• Large disk has larger angular acceleration.
• Smaller disk has larger angular acceleration.
