Question

Which of the following are true about centripetal force? Check all that apply. A. Without centripetal force, an object cannot accelerate. B. Friction can be a centripetal force, such as when it keeps a car on the road going around a curve. C. Gravity can be a centripetal force, such as when it pulls a satellite in its orbit. D. It's also called an outward force.

Answer 1

Centripital force is a center seeking force, meaning it is always directed to the center point of rotation.

A is vague, but true. Assuming there is no friction and an object is already in centripetal motion; without centripital force, there will be no acceleration. The centripital force is responsible for an acceleration which doesn't affect the magnitude of the object's velocity, but rather the change in direction of the velocity.

B is true. Friction keeps the car from sliding due to the tendency for the car to want to maintain a straight path. Thus it is responsible for allowing the car to execute a turn by causing a center seeking force to the center of the point of the curve.

C is true. Newton's law of gravitation states that there is an attraction force between two masses. If a mass is undergoing an orbit around another mass, the gravitation force of attraction is responsible for maintaining the object's orbit.

D. This is false, as stated above and exemplified, centripital force is a center seeking force.

Answer 2

B. Friction can be a centripetal force, such as when it keeps a car on the road going around a curve.

C. Gravity can be a centripetal force, such as when it pulls a satellite in its orbit.

Explanation:

The centripetal force is any force that keeps an object moving in circular motion, "pulling" the object towards the centre of the circular trajectory.

Several forces can act as centripetal force. Examples are:

- friction: when a car is going around the curve, is moving by circular motion. The force that keeps the car in circular motion is, in fact, the friction between the tires and the road.

- Gravity: when a satellite moves around the Earth, it is moving by circular motion. The force that keeps the satellite in circular motion is the gravitational attraction between the Earth and the satellite, that pushes the satellite towards the Earth.

The other two options are not correct because:

A) An object can also accelerate if there is no centripetal force (for example, a car speeding up on a straight road is accelerating, but there is no centripetal force since there is no circular motion

D) Centripetal force is not an outward force, since it pushes the object inwards (towards the centre of the trajectory).