Rocket activity Original worksheet was produced by Philip Anthony


DEFINITION OF TERMS Maximum height of rocket = H + h Mass of rocket before firing = m_{i} Mass of rocket after fuel is exhausted = m_{f} Time from A to C (stopwatch) = t_{AC} Time from A to B = t_{AB} Time from B to C = t_{BC} Average drag from B to C = F_{BC} Vertical component of AB = x_{AB} Vertical component of BC = x_{BC} Distance between observers = D Sight angles of observers = X1 , X2 Speed of rocket at B = v_{B} 


A. Calculating an Estimate of x_{AB}  
• Measure m_{i} on an electronic balance  
• Launch the rocket and measure t_{AC} , X1^{0} , X2^{0} 

• Measure m_{f} on an electronic balance.  
The manufacturers quote the impulse and thrust delivered by an “A83” rocket motor as being respectively 2.5 N s and 13.6 N.  
• What value does this give for t_{AB} ? Hint  
• What is the mean mass of the rocket as it moves from A to B? Hint  
Hide hint (m_{f} + m_{i} ) = mean mass
The combination of all forces acting on an object is known as the net force. It is the net force that changes an object's state of motion. Hide the hint 

Click to hide hint
The quantity
Force X time interval
is known as impulse.
impulse = thrust X time
Given the thrust and the impulse of an engine we can calculate the time
interval over which the engine produces thrust.
Impulse/thrust = time in seconds.