An object is dropped from rest. What is its instantaneous speed when it has
been in motion for 3 s? The acceleration of
gravity is 9.8 m/s
2
.
Answer in units of m/s.

29.4m/s

Explanation:

Given parameters:

Duration of motion  = 3s

Acceleration due to gravity  = 9.8m/s²

Unknown:

Instantaneous speed  = ?

Solution:

Instantaneous speed is the speed at an instant or a particular time.

 Since initial speed = 0 because it was at rest, the best motion equation to solve this problem is given as;

    V = U + gt

Where V is the instantaneous speed

           U is the initial speed

           g is the acceleration due to gravity

            t is the time taken

Insert the parameters and solve;

        V = 0 + 9.8 x 3  = 29.4m/s

answer: 2×10^-2kg

explanation: density= mass per volume

vol=mass/density

converting to s.i units we have;

3÷1000kg = 0.003

1.5÷100m = 0.15

0.003/0.15 = 0.02kg