AIBU to ask for help with a Maths question?

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DD is struggling with an A-Level Maths question about Projectiles. She has got the answer in the text book as 69.5 degrees. She just doesn't understand how this answer is arrived at. I have attached a photo of the question.

Does anyone have any ideas?

Thanks in advance for any suggestions.

Sounds like you need a mechanics expert, was my favourite part of A level maths but I’ve forgotten all of it. I’m pretty sure it’ll involve integration though.

I'm feeling really hopeless that I can't remember this.

I feel as if it needs to be something about:

• the horizontal speed is initially 35cos&
• the initial vertical speed is initially 35sin&
• the time taken to travel the 80m has to equal the time you need to have also travelled 5m total vertically (though obviously way more up and down)

I also feel as is s=ut+1/2at^2 is likely to come into it somewhere (where acceleration is g)

Not convinced that integration comes into it.

Happy to be corrected and to see the proper answer from someone who hasn't forgotten their basic A level maths/physics.

DD is just going out but says that she'll do it later if you still need help.

about 25.40 a very similar question is explained so should help her understand

You need x=ut cosa and y=ut sina - 1/2gt^2

Plug in the numbers you know (x,y,u)

then you can solve the 2 equations for a and t
It's probably easiest to find cos a and sin a in terms of t and then use the trig identity cos2 a + sin2 a = 1 to eliminate a.

Then you can solve remaining equation for t and plug it back in to find a

Thank you Lee I have clearly forgotten less than I feared.

ps unlikely to land in hole due to air resistance, wind conditions, accuracy of direction of shot etc.

1. Calculate initial horizontal and vertical components of the motion as a function of the angle using trigonometry.
2. Vertically: the ball will be decelerating then accelerated due to gravity.

a. Work out an equation for how high the ball goes using equations of motion, and one for how long it takes to reach that height. b. Then an equation how long it takes to fall from the peak height to the ground (remember to minus the 5m). c. Combine these 2 for an equation for how long the ball is in the air.

1. Horizontally you want the ball to travel a distance of 80m in the time the ball is in the air.
2. You should have 2 equations to solve with the angle and the time as the unknowns.

Don’t forget to use the correct sign (+/-) for the gravity term!

Hope that helps!

Thank you so much. I will relay info to DD who will be very grateful.

But did the golfer get the ball to where they wanted?

Did DD manage to answer the question?

@MumW

Did DD manage to answer the question?

Thank you to you lot she now understands how to get to the answer. The text book had the answer in but no workings out. She didn't understand how to arrive at the answer but now does thanks to you lovely lot!

My only response is "Qué?"

@joystir59

My only response is "Qué?"

Know what you mean! I didn't go beyond O-Level maths so can't help DD myself!

I took 3 attempts to pass o level maths, and still struggle with multiplying fractions!