Physics Mechanics 1 — Questions and Answers
Question 1: A car accelerates uniformly from rest to a speed of 20 m/s in 5 seconds. What is the car’s acceleration?
- 2 m/s²
- 4 m/s² (Correct answer)
- 5 m/s²
- 10 m/s²
Correct answer: 4 m/s²
Acceleration is calculated using the formula 𝑎=Δ𝑣/𝑡 a= 5s 20m/s−0m/s=4m/s 2 /2 .
Question 2: A 10 kg object is pushed with a net force of 50 N. What is its acceleration?
- 2 m/s²
- 5 m/s² (Correct answer)
- 10 m/s²
- 50 m/s²
Correct answer: 5 m/s²
From Newton’s Second Law, 𝐹=𝑚a, rearrange to 𝑎=𝐹/𝑚. a= 50N/ 10kg =5m/s 2. . .
Question 3: A 2 kg ball moving at 3 m/s collides with a stationary 1 kg ball. After the collision, the 2 kg ball moves at 1 m/s. What is the velocity of the 1 kg ball if the collision is perfectly elastic?
- 2 m/s (Correct answer)
- 3 m/s
- 4 m/s
- 6 m/s
Correct answer: 2 m/s
In a perfectly elastic collision, momentum is conserved. Initial momentum: Solve for v: 6=2+v,v=4m/s.
Question 4: A 5 kg object is dropped from a height of 20 m. Ignoring air resistance, what is its velocity just before hitting the ground? (Take 𝑔=9.8m/s2 ).
- 14 m/s
- 20 m/s
- 28 m/s (Correct answer)
- 40 m/s
Correct answer: 28 m/s
Use the equation for free fall, v= 2gh: v= 2⋅9.8⋅20= 392 ≈28m/s.
Question 5: A block slides down a frictionless incline of height 5 m. What is its speed at the bottom? (Take 𝑔=9.8m/s2).
- 5 m/s
- 9.8 m/s
- 10 m/s (Correct answer)
- 15 m/s
Correct answer: 10 m/s
The potential energy at the top is converted into kinetic energy at the bottom: mgh= 1/2 mv 2 ⟹v= 2gh .Substitute: 𝑣=2⋅9.8⋅5=98≈10m/s.
Physics Mechanics 1
A car accelerates uniformly from rest to a speed of 20 m/s in 5 seconds.
What is the car’s acceleration?