W=F*s
W=9000*0
W=0
W:Work
F:Force
s:Distance
        
             
        
        
        
Answer:
A. Endothermic reaction. 
B. +150KJ. 
C. 250KJ. 
Explanation:
A. The graph represents endothermic reaction because the heat of the product is higher than the heat of the reactant.
B. Determination of the enthalpy change, ΔH for the reaction. This can be obtained as follow:
Heat of reactant (Hr) = 50KJ
Heat of product (Hp) = 200KJ
Enthalphy change (ΔH) =..?
Enthalphy change = Heat of product – Heat of reactant.
ΔH = Hp – Hr
ΔH = 200 – 50
ΔH = +150KJ 
Therefore, the enthalphy change for the reaction is +150KJ
C. The activation energy for the reaction is the energy at the peak of the diagram. 
From the diagram, the activation energy is 250KJ.
 
        
             
        
        
        
Both oceanic and continental crust.
I hope this helps!
        
                    
             
        
        
        
Answer:
C. At a particular instant
Explanation:
Speed is the defined as the ratio between the distance covered by an object and the time taken:

where d is the distance and t the time.
However, there are two possible measurements of speed:
- Average speed: this is the speed measured over a non-zero time interval (for example: a car moving 100 metres in 5 seconds; its average speed is

- Instantaneous speed: this is the speed of an object measured at a particular instant in time, so for a time interval that tends to zero. So, in the previous example, the average speed is 20 m/s but the instantaneous speed of the car at various instants of time can be different from that value.
 
        
             
        
        
        

Explanation:
At the top of the tree, the velocity of the pebble is purely horizontal so we can calculate it as

