# As Physics

posted by cake

Use the equations below:
P=mv
Ek=1/2mv^2
4) A wooden target of mass 2.00kg is suspended from a branch so that it swings freely. The target is hit by an arrow of mass 0.10kg travelling horizontally and the arrow embeds itself in the centre of the target. The target swings upwards, with its centre of mass rising by 0.60m. Use 9.81 as the acceleration for gravity.

A) Calculate the gain in gravitational energy by the target and arrow combination.
B) Calculate the velocity of the arrow and target immediately after the impact.
C) Calculate the velocity of the arrow immediately before the impact.
D) Determine if the collision is elastic or inelastic and why.
12 marks

This one is a really tricky one so please write out in full, and no symbols please as i dont understand when you do that just full words

1. Damon

I find it difficult to do algebra without symbols.

gain in potential energy = m g h
= 2.1 * 9.81 * 0.60 Joules
= 12.4 Joules

kinetic energy before = gain in potential energy
(1/2)(2.1)v^2 = 12.4 Joules
v = 3.43 m/s

momentum before collision = momentum after
0.1 * u = 2.1 * v
u = 72 m/s

It is inelastic
show that (1/2)(2.1)(3.43^2) = 12.4 is less than (1/2)(.1)(72^2) = 260 Joules
In other words most of the kinetic energy of the arrow was dissipated as heat during the collision.

2. Writeacher

From yesterday -- https://www.jiskha.com/display.cgi?id=1512471691

It looks as if "cake" needs to learn the common symbols used in math and physics:

https://en.wikipedia.org/wiki/List_of_common_physics_notations

http://jick.net/symbols/Math.html

https://en.wikipedia.org/wiki/Greek_letters_used_in_mathematics,_science,_and_engineering

3. Writeacher

PS -- "learn" means "memorize"!

4. bobpursley

I also suggest any of these basic concept books: They should be available in the UK. https://www.amazon.com/Physics-Dummies-Math-Science/dp/1119293596

5. cake

Thank you so much Damon I understand all of what you have written it is so clear and thank you for the tips writeacher and the useful websites as we don use any of the symbol in my class we just use full words and numbers and just mostly talk though how to do it. Thanks again Damon

6. cake

Thank you Damon for your reliability and not making fun of me not knowing some symbols.

7. Writeacher

No one's making fun. Just trying to give you the information you need to keep progressing!

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