C.
The train first sped up, giving it a positive acceleration in the beginning. This eliminates D since that choice states that it begins with a negative acceleration. This also eliminates B since that choice states that the train only had a negation acceleration.
Next, the train slows down, giving it a negative acceleration. We’re looking for the answer choice that starts with a positive acceleration and ends with a negative one. This makes C the correct answer. Hope this helps!
Answer:
C.
Explanation:
If we look at the equation x(final) = v(initial)*t + x(initial), where v(initial in the x dir.) in the same both times, and x(initial) is 0, we can conclude that t is responsible for the change in x(final).
First object:
m=10 kg
F=20 N
F=ma, then:
a=F/m
a=20/10=2 m/s²
Second object:
m=18 kg
F=30 N
a=F/m
a=30/18=1.6 m/s²
The first object has a higher acceleration.
The formula for working out speed is distance ÷ time.
55 km ÷ 2 hours = 27.5 km/h (average speed for first part of journey)
52km ÷ 5 hours = 10.4 km/h (average speed for second part of journey)
(27.5 + 10.4) ÷ 2 = 18.95 km/h (average speed throughout the journey)
Answer:
4200 kJ
10 kg/min
Explanation:
70 kW means 70 kJ per second. So in a minute, the amount of heat generated at the brake is:
70 kJ/s × 60 s/min = 4200 kJ
Heat = mass × specific heat capacity × increase in temperature
4200 kJ = m × 4.184 kJ/kg/C × 100 C
m = 10 kg
So every minute, 10 kg of water is heated. So the mass flow is 10 kg/min.
