Why does an object moving in a circular path at constant speed still experience an acceleration?

Although the speed is constant, the direction of velocity is continuously changing, which constitutes a change in velocity and therefore an acceleration.

Explain why an object in uniform circular motion has zero tangential acceleration but non-zero centripetal acceleration.

The speed is constant so there is no acceleration along the direction of motion (tangential), but the velocity direction changes continuously, requiring an acceleration directed towards the centre.

Why is centripetal force not a separate type of force but rather a description of the role a force plays?

Centripetal force describes any force (such as tension, friction, or gravity) that acts towards the centre of a circular path to maintain circular motion; it is not a distinct force in itself.

In what direction does centripetal force act?

Towards the centre of the circular path.

What is the direction of centripetal acceleration?

Towards the centre of the circular path.

AQA A-Level Physics 7408

Measurements and Their Errors

Topic overview Use of SI units and their prefixes Limitation of physical measurements Estimation of physical quantities

Particles and Radiation

Topic overview Constituents of the atom Stable and unstable nuclei Particles, antiparticles and photons Particle interactions Classification of particles Quarks and antiquarks Applications of conservation laws The photoelectric effect Collisions of electrons with atoms Energy levels and photon emission Wave-particle duality

Waves

Topic overview Progressive waves Longitudinal and transverse waves Principle of superposition of waves and formation of stationary waves Interference Diffraction Refraction at a plane surface

Mechanics and Materials

Topic overview Scalars and vectors Moments Motion along a straight line Projectile motion Newton's laws of motion Momentum Work, energy and power Conservation of energy Bulk properties of solids The Young modulus

Electricity

Topic overview Basics of electricity Current–voltage characteristics Resistivity Circuits Potential divider Electromotive force and internal resistance

Further Mechanics and Thermal Physics

Topic overview Circular motion Simple harmonic motion (SHM)Simple harmonic systems Forced vibrations and resonance Thermal energy transfer Ideal gases Molecular kinetic theory model

Fields and Their Consequences

Topic overview Fields Newton's law Gravitational field strength Gravitational potential Orbits of planets and satellites Coulomb's law Electric field strength Electric potential Capacitance Parallel plate capacitor Energy stored by a capacitor Capacitor charge and discharge Magnetic flux density Moving charges in a magnetic field Magnetic flux and flux linkage Electromagnetic induction Alternating currents Transformers

Nuclear Physics

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Topic overview Astronomical telescope consisting of two converging lenses Reflecting telescopes Single dish radio telescopes, I-R, U-V and X-ray telescopes Advantages of large diameter telescopes Classification by luminosity Absolute magnitude, M Classification by temperature, black-body radiation Principles of the use of stellar spectral classes The Hertzsprung-Russell (HR) diagram Supernovae, neutron stars and black holes Doppler effect Hubble's law Quasars Detection of exoplanets

Medical PhysicsOptional topic

Engineering PhysicsOptional topic

Topic overview Concept of moment of inertia Rotational kinetic energy Rotational motion Torque and angular acceleration Angular momentum Work and power First law of thermodynamics Non-flow processes The p–V diagram Engine cycles Second Law and engines Reversed heat engines

Turning Points in PhysicsOptional topic

Topic overview Cathode rays Thermionic emission of electrons Specific charge of the electron Principle of Millikan's determination of the electronic charge, e Newton's corpuscular theory of light Significance of Young's double slits experiment Electromagnetic waves The discovery of photoelectricity Wave–particle duality Electron microscopes The Michelson-Morley experiment Einstein's theory of special relativity Time dilation Length contraction Relativistic mass and energy

ElectronicsOptional topic

Topic overview MOSFET (metal-oxide semiconducting field-effect transistor)Zener diode Photodiode Hall effect sensor Difference between analogue and digital signals LC resonance filters The ideal operational amplifier Inverting amplifier configuration Non-inverting amplifier configuration Summing amplifier configuration Real operational amplifiers Combinational logic Sequential logic Astables Principles of communication systems Transmission media Time-division multiplexing Amplitude (AM) and frequency modulation (FM) techniques

Further Mechanics and Thermal Physics

Circular motion

7 things to know
Papers 2 and 3

Overview

Angular speed, centripetal acceleration and centripetal force, and what supplies it.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Numbers

What is angular speed, and how does it relate to linear speed and to frequency?

Numbers

What unit is angular speed measured in, and how is centripetal acceleration calculated?

Numbers

What do the terms in a = ω²r mean, and what happens to a if ω is doubled, or if r is doubled at constant ω?

Numbers

How is centripetal force calculated from linear and from rotational quantities?

Numbers

How is angular speed found from frequency, and what does halving the mass do to the force?

Key term

How many radians are there in one complete revolution?

Key term

What is required for an object to maintain motion in a circular path at constant speed?

Questions from this subtopic

Each one with the model answer underneath.

1
Why does an object moving in a circular path at constant speed still experience an acceleration?
Model answer
Although the speed is constant, the direction of velocity is continuously changing, which constitutes a change in velocity and therefore an acceleration.
2
Explain why an object in uniform circular motion has zero tangential acceleration but non-zero centripetal acceleration.
Model answer
The speed is constant so there is no acceleration along the direction of motion (tangential), but the velocity direction changes continuously, requiring an acceleration directed towards the centre.
3
What is required for an object to maintain motion in a circular path at constant speed?
Model answer
A centripetal force is required.
4
Why is centripetal force not a separate type of force but rather a description of the role a force plays?
Model answer
Centripetal force describes any force (such as tension, friction, or gravity) that acts towards the centre of a circular path to maintain circular motion; it is not a distinct force in itself.
5
In what direction does centripetal force act?
Model answer
Towards the centre of the circular path.
6
What is the direction of centripetal acceleration?
Model answer
Towards the centre of the circular path.

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