1) A The 78g
2) C Push on the wagon in the opposite direction as Jack with a force that is the same as Jack is applying.
Answer:
Explanation:
mass of sled, m = 22 kg
Force of pull, F = 31 N
distance move, d = 53 m
Angle between force and distance, θ = 40°
The formula for the work done is
W = F x d x Cos θ
W = 31 x 53 x cos 40
W = 1258.6 J
Answer:
A. when the mass has a displacement of zero
Explanation:
The velocity of a mass on a spring can be calculated by using the law of conservation of energy. In fact, the total energy of the mass-spring system is equal to the sum of the elastic potential energy (U) of the spring and the kinetic energy (K) of the mass:

where
k is the spring constant
x is the displacement of the mass with respect to the equilibrium position of the spring
m is the mass
v is the velocity of the mass
Since the total energy E must remain constant, we can notice the following:
- When the displacement is zero (x=0), the velocity must be maximum, because U=0 so K is maximum
- When the displacement is maximum, the velocity must be minimum (zero), because U is maximum and K=0
Based on these observations, we can conclude that the velocity of the mass is at its maximum value when the displacement is zero, so the correct option is A.
Answer: Option 2
Explanation:
Option 1 is wrong because there are 2 protons and 2 neutrons in nucleus.
Option 3 is wrong because there are two electrons moving around nucleus.
Option 4 is wrong because electrons are negatively charged and are moving around the nucleus.
Option 5 is wrong because there equal amount of protons and electrons with 2 each.