Finding acceleration?

Question

I have the question...

"A jet-ski starts from rest and accelerates uniformly. If it travels 2m in it's first second, find it's acceleration?"

I keep getting 2ms^-2 for the answer, but the answer in the back of the book says 4ms^-2. How do I get this answer?

Answer 1

position = x_0 + v_0(t) + (1/2)a t^2

Now x_0 = 0 and v_0 = 0 so the equation of motion is:

p = (1/2)a t^2 putting 2 m in for p and 1 in for t gives

2 = (1/2)a

a = 4 m/s^2

Hope this helps.

It's a great idea to memorize the general equation for motion under constant acceleration which is:

p(t) = x_0 + v_0(t) + (1/2)(a)t^2

where x_0 is initial position and v_0 is initial velocity.

Hope this helps!

Answer 2

draw a triangle to represent a velocity (vertical axis) vs time (horizontal axis.  the area of this triangle is the distance(2m) The slope of the line is the acceleration. Use the rule for area of a triangle and the height of this triangle is 4. to get the slope use rise over run (4 over 1)  

Answer 3

S=ut +1/2 a t^2

2=0 +1/2 * a * 1

2=a/2

a=4