The hammer throw is a track-and-field event in which a 7.30-kg ball (the hammer) is whirled around in a circle several times and released. it then moves upward on the familiar curved path of projectile motion and eventually returns to the ground some distance away. the world record for the horizontal distance is 86.75 m, achieved in 1986 by yuriy sedykh. ignore air resistance and the fact that the ball was released above the ground rather than at ground level. furthermore, assume that the ball is whirled around a circle that has a radius of 1.68 m and that its velocity at the instant of release is directed 33.9 ° above the horizontal. find the magnitude of the centripetal force acting on the ball just prior to the moment of release.

the velocity you are looking for is made up of two parts: horizontally velocity, vh, and its vertical velocity, vv. the actual velocity of the ball will be these two parts added together, and because velocity is a vector then they will need to be added vectorially.  

neglecting air resistance etc etc.,  

the horizontal velocity component will be constant (because there is no accelerating force in the horizontal direction.  

vh = 8 ms-1  

the vertical velocity component has an accelerating force: 'g'.  

using v = u +at where a = g = 9.81 ms-2.  

the vertical component of velocity, vv = 0 + gt = vv =9.81 x 2  

vv = 19.62 ms-1 . the zero appears because the virtical component of velocity at time t=0 is zero. remember, the ball was thrown horizontally.  

how fast it will be moving (it actual path (being a parabola )) will be the vector sum of these two.  

adding vectorally gives: -  

v = sqr root (8^2 + 19.62^2) = sqr root(64+384.9) = 21.18 or 21.2 ms-1

answer: option c. i.e. electric current flowing “downhill” from the negative electrode to the positive electrode in a battery

explanation:

the water analogy to the circuits define the pipes (water flows) to the electric current. now, we know that the electric current flows from the positive terminal to the circuit (as shown in the diagram attached).

hence, option c is the correct answer.

the diagram which shows forces as either balanced = same speed or unbalanced = accelerarting

explanation:

as the height from which the ruler was dropped increased, the speed of the ruler at ryan's hand increased.