Question

A 2kg object is dropped from a height 10m.Calculate the speed of the object after it has fallen 5m, assuming there is no resistance. g= 10 N/kg​

Answer 1

The kinetic energy the object has at any point during the fall is exactly the potential energy it lost by falling to that height.

Potential energy = (mass) · (gravity) · (height)

Change of potential energy = (mass) · (gravity) · (change of height)

Change of potential energy = (2 kg) · (10 m/s ) · (-5 m)

Change of potential energy = 100 Joules

Kinetic energy = (1/2) · (mass) · (speed²)

Kinetic energy = (1 kg) · (speed² )

100 J = (1 kg) · (speed²)

Speed² = (100 J) / (1 kg)

Speed² = (100 kg-m²/s²) / (1 kg)

Speed² = (100 m²/s²)

Speed = 10 m/s  

Answer 2

Answer:

10m/s

Explanation:

$d=v_ot+\dfrac{1}{2}at^2$

Since there is no initial velocity as the object is dropped, you can write the following equation:

$5=\dfrac{1}{2}(10)t^2 \\\\1=t^2 \\\\t=1$

Now that you know how long the fall took, you can use another physics equation to find the velocity at that point.

$v_f=v_o+at$

Since there once again is no initial velocity, you can rewrite this as:

$v_f=at=(10)(1)=10m/s$

Hope this helps!