Answer:
(a) The horizontal ground reaction force 
(b) The vertical ground reaction force 
(c) The resultant ground reaction force 
Explanation:
Given
John mass , m = 65 kg
Horizontal acceleration , 
Vertical acceleration , 
(a) Using Newton's 2nd law in horizontal direction
=>
Thus the horizontal ground reaction force
(b) Using Newton's 2nd law in vertical direction
=>
=>
Thus the vertical ground reaction force
(c) Resultant ground reaction force is
=>
=>
Thus the resultant ground reaction force
Answer: 2000 watts
Explanation:
Given that,
power = ?
Weight of object = 200-N
height = 4 m
Time = 4 s
Power is the rate of work done per unit time i.e Power is simply obtained by dividing work by time. Its unit is watts.
i.e Power = work / time
(since work = force x distance, and weight is the force acting on the object due to gravity)
Then, Power = (weight x distance) / time
Power = (200N x 4m) / 4s
Power = 8000Nm / 4s
Power = 2000 watts
Thus, 2000 watts of power is needed to lift the object.
Explanation:
Acceleration is the change in speed over change in time.
a = Δv / Δt
a. The car's acceleration is:
a = (80 km/h − 0 km/h) / 10 s
a = 8 km/h/s
So every second, the speed increases by 8 km/h.
b. The cyclist's acceleration is:
a = (16 m/s − 4.0 m/s) / 5.6 s
a = 2.1 m/s²
c. The stone's speed is:
10.0 m/s² = (v − 0 m/s) / 3.5 s
v = 35 m/s
d. The time is:
1.6 m/s² = (10 m/s − 0 m/s) / t
t = 6.3 s
The wind Wind turbines work on a simple principle: instead of using electricity to make wind—like a fan—wind turbines use wind to make electricity. Wind turns the propeller-like blades of a turbine around a rotor, which spins a generator, which creates electricity.
