EmSAT Physics 5

Question 1

A car decelerates uniformly from 30 m/s to rest over a distance of 90 m. What is the magnitude of the deceleration?

Accepted Answer

5 m/s²

Answer

Using v² = u² – 2as: 0 = 900 – 2a(90) → a = 900/180 = 5 m/s².

Question 2

According to the law of conservation of momentum, when two objects collide and stick together, the total momentum:

Accepted Answer

Is conserved

Answer

In any collision with no external forces, total momentum before equals total momentum after (conservation of momentum).

Question 3

The efficiency of a machine is 80%. If the input power is 500 W, what is the useful output power?

Accepted Answer

400 W

Answer

Output power = efficiency × input power = 0.80 × 500 = 400 W.

Question 4

Which process transfers heat without requiring a medium?

Accepted Answer

Radiation

Answer

Radiation transfers energy via electromagnetic waves and can travel through a vacuum, unlike conduction or convection.

Question 5

A photon has an energy of 3 eV. What is its approximate frequency? (h = 4.14 × 10⁻¹⁵ eV·s)

Accepted Answer

7.25 × 10¹⁴ Hz

Answer

f = E/h = 3 / (4.14 × 10⁻¹⁵) ≈ 7.25 × 10¹⁴ Hz, which falls in the visible light range.

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