FREE Physics Mechanics Questions and Answers
A car accelerates uniformly from rest to a speed of 20 m/s in 5 seconds. What is the car’s acceleration?
Correct!
Wrong!
Acceleration is calculated using the formula 𝑎=Δ𝑣/𝑡 a= 5s 20m/s−0m/s=4m/s 2 /2 .
A 10 kg object is pushed with a net force of 50 N. What is its acceleration?
Correct!
Wrong!
From Newton’s Second Law, 𝐹=𝑚a, rearrange to 𝑎=𝐹/𝑚. a= 50N/ 10kg =5m/s 2. . .
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?
Correct!
Wrong!
In a perfectly elastic collision, momentum is conserved. Initial momentum: Solve for v: 6=2+v,v=4m/s.
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 ).
Correct!
Wrong!
Use the equation for free fall, v= 2gh: v= 2⋅9.8⋅20= 392 ≈28m/s.
A block slides down a frictionless incline of height 5 m. What is its speed at the bottom? (Take 𝑔=9.8m/s2).
Correct!
Wrong!
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.