I throw a ball against a wall, so that at the moment it hits, it is moving horiz
ID: 1619852 • Letter: I
Question
I throw a ball against a wall, so that at the moment it hits, it is moving horizontally and has momentum p. Right after it bounces the wall, it's moving in exactly the opposite direction with momentum p (the same, in other words). How much impulse did the wall transfer to the ball? i) 0 ii) p/2 iii) p iv) 2p Why? (b) A person throws three identical rocks off a cliff height h with exactly the same speed in as shown above. Rock A is thrown almost vertically upwards, rock C almost vertically downwards, and rock B horizontally. Which rock hits the ground at the greatest speed (ignoring air resistance)? i) Rock A ii) Rock B ii) Rock C iv) They all hit at the same speed Why? (c) Still looking at the figure above, after the rooks leave the person's hand, which one has the largest acceleration? i) Rock A ii) Rock B ii) Rock C iv) The acceleration of the three rocks are the same. Why?Explanation / Answer
(2a)impulse= change in momentum
i= pi- pf
initial momentum=p
final momentum= -p as it changes direction
i= -p-p=-2p
i= 2p.
(b) here the potential energy is converted into kinetic energy as the objects fall. Height for all is same.also initial speed is sme for all.so all of the objects hit the ground with the same speed.
(c)All the three rocks are falling under the effect of gravity. so acceleration for all of them is same and is equal to acceleration due to gravitatio= g= -9.8m/s^2