Answer:84.672 joules.
Explanation:
1) Data:
m = 7.2 kg
h = 1.2 m
g = 9.8 m / s²
2) Physical principle
Using the law of mechanical energy conservation principle, you have that the kinetic energy of the dog, when it jumps, must be equal to the final gravitational potential energy.
3) Calculations:
The gravitational potential energy, PE, is equal to m × g × h
So, PE = m × g × h = 7.2 kg × 9.8 m/s² × 1.2 m = 84.672 joules.
And that is the kinetic energy that the dog needs.
Answer:
2.5 x 10⁷ J
Explanation:
F = thrust of the engine = 2.3 x 10⁵ N
d = distance traveled = 87 m
Work done by the engine is given as
W = F d = (2.3 x 10⁵) (87) = 200.1 x 10⁵ J
W' = Net work done
W'' = work done by catapult
KE₀ = initial kinetic energy = 0 J
KE = final kinetic energy = 4.5 x 10⁷ J
Net work done is given as
W' = KE - KE₀
W' = 4.5 x 10⁷ J
We know that
W' = W + W''
4.5 x 10⁷ = 2.001 x 10⁷ + W''
W'' = 2.5 x 10⁷ J
Since force is mass*acceleration,
F = 70kg * 9.8 m/s
