Physics Mechanics

Question 1

A car accelerates uniformly from rest to a speed of 20 m/s in 5 seconds. What is the car’s acceleration?

Accepted Answer

4 m/s²

Answer

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?

Accepted Answer

5 m/s²

Answer

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?

Accepted Answer

2 m/s

Answer

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 ).

Accepted Answer

28 m/s

Answer

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).

Accepted Answer

10 m/s

Answer

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 Practice Test

Physics Practice Test

Physics Mechanics