A resistor of 3 Ω has 14 V across it. Enter the current in amperes.
Correct Answer: 4.667
Explanation:
Ohm’s law gives I=V/R=14/3=4.667 A.
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Enter the kinetic energy of a 4 kg object moving at 2 m/s.
Correct Answer: 8
Explanation:
K=½mv²=½×4×2²=8.0 J.
A net force accelerates a 2 kg mass at 2 m/s². Enter the force in newtons.
Correct Answer: 4
Explanation:
Newton’s second law gives F=ma=2×2=4 N.
An object travels 260 m in 10 s at constant speed. Enter its speed in m/s.
Correct Answer: 26
Explanation:
Speed=distance/time=260/10=26.00 m/s.
Practice context 7: Which statement correctly defines radioactive half-life?
Choose an option to check your answer.
Correct Answer: D. The half-life is the time for the number of undecayed nuclei to fall to half its initial value
Explanation:
Half-life is a characteristic decay time at which the undecayed population becomes one half.
Practice context 7: Which statement about a thin convex lens is correct?
Choose an option to check your answer.
Correct Answer: B. A convex lens can converge parallel rays to a real focus
Explanation:
A convex lens is converging and brings parallel incident rays toward its principal focus.
Practice context 7: Which definition of electric-field direction is correct?
Choose an option to check your answer.
Correct Answer: D. The electric field points in the direction a positive test charge would accelerate
Explanation:
Electric-field direction is defined by the force direction on a positive test charge.
Practice context 7: For a transverse wave, how is the oscillation direction related to propagation?
Choose an option to check your answer.
Correct Answer: D. It is perpendicular to the direction of wave propagation
Explanation:
A transverse wave oscillates perpendicular to the direction in which the wave travels.
Practice context 7: Which statement correctly expresses conservation of momentum?
Choose an option to check your answer.
Correct Answer: C. The total momentum of an isolated system remains constant
Explanation:
In an isolated system, internal forces occur in equal and opposite pairs, so total momentum is constant.
A wave has frequency 9 Hz and wavelength 2 m. Enter its speed.
Correct Answer: 18
Explanation:
Wave speed v=fλ=9×2=18 m/s.
A resistor of 2 Ω has 13 V across it. Enter the current in amperes.
Correct Answer: 6.5
Explanation:
Ohm’s law gives I=V/R=13/2=6.500 A.
Enter the kinetic energy of a 3 kg object moving at 9 m/s.
Correct Answer: 121.5
Explanation:
K=½mv²=½×3×9²=121.5 J.