Question
4) A partially filled bag of cement having a mass of 16.0kg falls 40.0m into a river from a bridge. a. What is the kinetic energy of the bag as it hits the water? b. What is its speed just before it hits the water? falls 64.0m. d. What is its new kinetic energy
Answer
4
(257 Votes)
Morris
Master · Tutor for 5 years
Answer
a. The kinetic energy of the bag as it hits the water is \( KE = \frac{1}{2} \times 16.0 \times (\sqrt{2 \times 9.8 \times 40.0})^{2} \) Joules.b. Its speed just before it hits the water is
m/s.
Explanation
## Step 1: Find the kinetic energyTo find the kinetic energy (KE) of the bag as it hits the water, we use the formula for kinetic energy:###
where
is the mass and
is the velocity. However, we don't know the velocity yet. To find the velocity, we can use the formula for the final velocity of an object in free fall:###
where
is the acceleration due to gravity (approximately
) and
is the height from which the object falls. ## Step 2: Calculate the velocitySubstituting
and
into the formula gives us:###
## Step 3: Calculate the kinetic energyNow we can substitute
and the calculated velocity into the kinetic energy formula to find the kinetic energy.