2: A cannon fires an 8 kg cannonball into the air. At the highest point in its flight, before coming back down, the cannonball has a horizontal velocity of 35 m/s and is 15 m above the ground.
We can think about the mechanics of the cannon's firing as follows: while the ball was in the 1.5 m
long tube, it experienced an average force due to the explosion of gunpowder. The moment the ball
left the tube, it started to free fall (that is, fly in projectile motion) since this force is no longer
applied. What average force did the cannon's gunpowder explosion apply to the cannonball while it
was in the tube?

For general projectile motion, when the projectile is at the highest point of its trajectory, its acceleration is zero? a)the horizontal and vertical components of its velocity are zero. b) its velocity is perpendicular to the acceleration. c)the horizontal component of its velocity is zero. d)its velocity and acceleration are both zero.

We want to calculate the total metabolic heat generated by a singing canary taking into account heat transfer by radiation, convection and exhaling air. the air temperature is 20 oc, canary’s body internal and surface temperature is 33oc, external body surface convective heat transfer coefficient is 25.2 w/m2 .k, temperature difference between the inhaled and exhaled air is 4.3 oc, the ventilation rate is 0.74 cc of air per second, specific heat of air is 1.0066 kj/kg. k and density of air is 1.16 kg/m3 . assume the canary’s body to be a cylinder with 7 cm diameter and 9 cm length, and heat exchange is from the side as well as the top and bottom of cylinder. calculate 1) the net rate of heat lost by radiation, assuming heat gained by the bird through radiation from the surroundings is 11.5 w; 2) rate of heat transferred by convection to the surrounding air; 3) rate of heat transferred in the exhaling air without considering any internal evaporation; 4) total metabolic power.

Convection currents are caused by differences in what two things?